Copyright © 1997, 1998, 1999, 2000 by the PHP Documentation Group
Copyright
This manual is © Copyright 1997, 1998, 1999, 2000 by the PHP Documentation Group. The members of this group are listed on the front page of this manual.
This manual can be redistributed under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
PHP, which stands for "PHP: Hypertext Preprocessor", is an HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly.
This manual is written in XML using the DocBook XML DTD, using DSSSL (Document Style and Semantics Specification Language) for formatting. The tools used for formatting HTML, TeX and RTF versions are Jade, written by James Clark and The Modular DocBook Stylesheets written by Norman Walsh. PHP's documentation framework is maintained by Stig Sζther Bakken.
Daily HTML snapshots of the manual, including translations, can be found at http://snaps.php.net/manual/.
PHP (officially "PHP: Hypertext Preprocessor") is a server-side HTML-embedded scripting language.
Simple answer, but what does that mean? An example:
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Example 1-1. An introductory example
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Notice how this is different from a CGI script written in other languages like Perl or C -- instead of writing a program with lots of commands to output HTML, you write an HTML script with a some embedded code to do something (in this case, output some text). The PHP code is enclosed in special start and end tags that allow you to jump into and out of PHP mode.
What distinguishes PHP from something like client-side Javascript is that the code is executed on the server. If you were to have a script similar to the above on your server, the client would receive the results of running that script, with no way of determining what the underlying code may be. You can even configure your web server to process all your HTML files with PHP, and then there's really no way that users can tell what you have up your sleeve.
At the most basic level, PHP can do anything any other CGI program can do, such as collect form data, generate dynamic page content, or send and receive cookies.
Perhaps the strongest and most significant feature in PHP is its support for a wide range of databases. Writing a database-enabled web page is incredibly simple. The following databases are currently supported:
Adabas D InterBase PostgreSQL dBase FrontBase Solid Empress mSQL Sybase FilePro (read-only) Direct MS-SQL Velocis IBM DB2 MySQL Unix dbm Informix ODBC Ingres Oracle (OCI7 and OCI8)
PHP also has support for talking to other services using protocols such as IMAP, SNMP, NNTP, POP3, HTTP and countless others. You can also open raw network sockets and interact using other protocols.
PHP was conceived sometime in the fall of 1994 by Rasmus Lerdorf. Early non-released versions were used on his home page to keep track of who was looking at his online resume. The first version used by others was available sometime in early 1995 and was known as the Personal Home Page Tools. It consisted of a very simplistic parser engine that only understood a few special macros and a number of utilities that were in common use on home pages back then. A guestbook, a counter and some other stuff. The parser was rewritten in mid-1995 and named PHP/FI Version 2. The FI came from another package Rasmus had written which interpreted html form data. He combined the Personal Home Page tools scripts with the Form Interpreter and added mSQL support and PHP/FI was born. PHP/FI grew at an amazing pace and people started contributing code to it.
It is difficult to give any hard statistics, but it is estimated that by late 1996 PHP/FI was in use on at least 15,000 web sites around the world. By mid-1997 this number had grown to over 50,000. Mid-1997 also saw a change in the development of PHP. It changed from being Rasmus' own pet project that a handful of people had contributed to, to being a much more organized team effort. The parser was rewritten from scratch by Zeev Suraski and Andi Gutmans and this new parser formed the basis for PHP Version 3. A lot of the utility code from PHP/FI was ported over to PHP3 and a lot of it was completely rewritten.
Today (end-1999) either PHP/FI or PHP3 ships with a number of commercial products such as C2's StrongHold web server and RedHat Linux. A conservative estimate based on an extrapolation from numbers provided by NetCraft (see also Netcraft Web Server Survey) would be that PHP is in use on over 1,000,000 sites around the world. To put that in perspective, that is more sites than run Netscape's flagship Enterprise server on the Internet.
Also as of this writing, work is underway on the next generation of PHP, which will utilize the powerful Zend scripting engine to deliver higher performance, and will also support running under webservers other than Apache as a native server module.
The source code, and binary distributions for some platforms (including Windows), can be found at http://www.php.net/.
This section will guide you through the configuration and installation of PHP. Prerequisite knowledge and software:
Basic UNIX skills (being able to operate "make" and a C compiler)
An ANSI C compiler
A web server
1. gunzip apache_1.3.x.tar.gz
2. tar xvf apache_1.3.x.tar
3. gunzip php-x.x.x.tar.gz
4. tar xvf php-x.x.x.tar
5. cd apache_1.3.x
6. ./configure --prefix=/www
7. cd ../php-x.x.x
8. ./configure --with-mysql --with-apache=../apache_1.3.x --enable-track-vars
9. make
10. make install
11. cd ../apache_1.3.x
12. for PHP 3: ./configure --activate-module=src/modules/php3/libphp3.a
for PHP 4: ./configure --activate-module=src/modules/php4/libphp4.a
13. make
14. make install
Instead of this step you may prefer to simply copy the httpd binary
overtop of your existing binary. Make sure you shut down your
server first though.
15. cd ../php-x.x.x
16. for PHP 3: cp php3.ini-dist /usr/local/lib/php3.ini
for PHP 4: cp php.ini-dist /usr/local/lib/php.ini
You can edit your .ini file to set PHP options. If
you prefer this file in another location, use
--with-config-file-path=/path in step 8.
17. Edit your httpd.conf or srm.conf file and add:
For PHP 3: AddType application/x-httpd-php3 .php3
For PHP 4: AddType application/x-httpd-php .php
You can choose any extension you wish here. .php is simply the one
we suggest.
18. Use your normal procedure for starting the Apache server. (You must
stop and restart the server, not just cause the server to reload by
use a HUP or USR1 signal.)
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PHP can be compiled in a number of different ways. Here is a quick summary:
./configure --with-apxs --with-pgsql
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This will create a libphp4.so shared library that is loaded into Apache using a LoadModule line in Apache's httpd.conf file. The PostgreSQL support is embedded into this libphp4.so library.
./configure --with-apxs --with-pgsql=shared
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This will again create a libphp4.so shared library for Apache, but it will also create a pgsql.so shared library that is loaded into PHP either by using the extension directive in php.ini file or by loading it explicitly in a script using the dl() function.
./configure --with-apache=/path/to/apache_source --with-pgsql
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This will create a libmodphp4.a library, a mod_php4.c and some accompanying files and copy this into the src/modules/php4 directory in the Apache source tree. Then you compile Apache using --activate-module=src/modules/php4/libphp4.a and the Apache build system will create libphp4.a and link it statically into the httpd binary. The PostgreSQL support is included directly into this httpd binary, so the final result here is a single httpd binary that includes all of Apache and all of PHP.
./configure --with-apache=/path/to/apache_source --with-pgsql=shared
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Same as before, except instead of including PostgreSQL support directly into the final httpd you will get a pgsql.so shared library that you can load into PHP from eihter the php.ini file or directly using dl().
To build PHP as an fhttpd module, answer "yes" to "Build as an fhttpd module?" (the --with-fhttpd=DIR option to configure) and specify the fhttpd source base directory. The default directory is /usr/local/src/fhttpd. If you are running fhttpd, building PHP as a module will give better performance, more control and remote execution capability.
The default is to build PHP as a CGI program. If you are running a web server PHP has module support for, you should generally go for that solution for performance reasons. However, the CGI version enables Apache users to run different PHP-enabled pages under different user-ids. Please make sure you read through the Security chapter if you are going to run PHP as a CGI.
PHP has native support for a number of databases (as well as ODBC):
--with-adabas=DIR
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Enables Adabas D support. The parameter is the Adabas D install directory and defaults to /usr/local/adabasd.
--with-filepro
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Enables the bundled read-only filePro support. No external libraries are required.
--with-ibm-db2=DIR
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Enables IBM DB2 support. The parameter to this option is the DB2 base install directory and defaults to /home/db2inst1/sqllib.
--with-msql=DIR
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Enables mSQL support. The parameter to this option is the mSQL install directory and defaults to /usr/local/Hughes. This is the default directory of the mSQL 2.0 distribution. configure automatically detects which mSQL version you are running and PHP supports both 1.0 and 2.0, but if you compile PHP with mSQL 1.0, you can only access mSQL 1.0 databases, and vice-versa.
See also mSQL Configuration Directives in the configuration file.
--with-mysql=DIR
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Enables MySQL support. The parameter to this option is the MySQL install directory and defaults to /usr/local. This is the default installation directory of the MySQL distribution.
See also MySQL Configuration Directives in the configuration file.
--with-iodbc=DIR
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Includes iODBC support. This feature was first developed for iODBC Driver Manager, a freely redistributable ODBC driver manager which runs under many flavors of UNIX. The parameter to this option is the iODBC installation directory and defaults to /usr/local.
--with-openlink=DIR
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Includes OpenLink ODBC support. The parameter to this option is the OpenLink ODBC installation directory and defaults to /usr/local/openlink.
--with-oracle=DIR
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Includes Oracle support. Has been tested and should be working at least with Oracle versions 7.0 through 7.3. The parameter is the ORACLE_HOME directory. You do not have to specify this parameter if your Oracle environment has been set up.
--with-pgsql=DIR
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Includes PostgreSQL support. The parameter is the PostgreSQL base install directory and defaults to /usr/local/pgsql.
See also Postgres Configuration Directives in the configuration file.
--with-solid=DIR
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Includes Solid support. The parameter is the Solid install directory and defaults to /usr/local/solid.
--with-sybase=DIR
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Includes Sybase support. The parameter is the Sybase install directory and defaults to /home/sybase.
See also Sybase Configuration Directives in the configuration file.
--with-sybase-ct=DIR
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Includes Sybase-CT support. The parameter is the Sybase-CT install directory and defaults to /home/sybase.
See also Sybase-CT Configuration Directives in the configuration file.
--with-velocis=DIR
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Includes Velocis support. The parameter is the Velocis install directory and defaults to /usr/local/velocis.
--with-custom-odbc=DIR
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Includes support for an arbitrary custom ODBC library. The parameter is the base directory and defaults to /usr/local.
This option implies that you have defined CUSTOM_ODBC_LIBS when you run the configure script. You also must have a valid odbc.h header somewhere in your include path. If you don't have one, create it and include your specific header from there. Your header may also require some extra definitions, particularly when it is multiplatform. Define them in CFLAGS.
For example, you can use Sybase SQL Anywhere on QNX as following: CFLAGS=-DODBC_QNX LDFLAGS=-lunix CUSTOM_ODBC_LIBS="-ldblib -lodbc" ./configure --with-custom-odbc=/usr/lib/sqlany50
--disable-unified-odbc
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Disables the Unified ODBC module, which is a common interface to all the databases with ODBC-based interfaces, such as Solid, IBM DB2 and Adabas D. It also works for normal ODBC libraries. Has been tested with iODBC, Solid, Adabas D, IBM DB2 and Sybase SQL Anywhere. Requires that one (and only one) of these modules or the Velocis module is enabled, or a custom ODBC library specified. This option is only applicable if one of the following options is used: --with-iodbc, --with-solid, --with-ibm-db2, --with-adabas, --with-velocis, or --with-custom-odbc.
See also Unified ODBC Configuration Directives in the configuration file.
--with-mcrypt
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Include support for the mcrypt library. See the mcrypt documentation for more information. If you use the optional DIR argument, PHP will look for mcrypt.h in DIR/include.
--enable-sysvsem
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Include support for Sys V semaphores (supported by most Unix derivates). See the Semaphore and Shared Memory documentation for more information.
--enable-sysvshm
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Include support for Sys V shared memory (supported by most Unix derivates). See the Semaphore and Shared Memory documentation for more information.
--with-xml
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Include support for a non-validating XML parser using James Clark's expat library. See the XML function reference for details.
--enable-maintainer-mode
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Turns on extra dependencies and compiler warnings used by some of the PHP developers.
--with-system-regex
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Uses the system's regular expression library rather than the bundled one. If you are building PHP as a server module, you must use the same library when building PHP as when linking the server. Enable this if the system's library provides special features you need. It is recommended that you use the bundled library if possible.
--with-config-file-path=DIR
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The path used to look for the configuration file when PHP starts up.
--with-exec-dir=DIR
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Only allow running of executables in DIR when in safe mode. Defaults to /usr/local/bin. This option only sets the default, it may be changed with the safe_mode_exec_dir directive in the configuration file later.
--enable-debug
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Enables extra debug information. This makes it possible to gather more detailed information when there are problems with PHP. (Note that this doesn't have anything to do with debugging facilities or information available to PHP scripts.)
--enable-safe-mode
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Enables "safe mode" by default. This imposes several restrictions on what PHP can do, such as opening only files within the document root. Read the Security chapter for more more information. CGI users should always enable secure mode. This option only sets the default, it may be enabled or disabled with the safe_mode directive in the configuration file later.
--enable-track-vars
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Makes PHP keep track of where GET/POST/cookie variables come from in the arrays HTTP_GET_VARS, HTTP_POST_VARS and HTTP_COOKIE_VARS. This option only sets the default, it may be enabled or disabled with the track_vars directive in the configuration file later.
--enable-magic-quotes
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Enable magic quotes by default. This option only sets the default, it may be enabled or disabled with the magic_quotes_runtime directive in the configuration file later. See also the magic_quotes_gpc and the magic_quotes_sybase directives.
--enable-debugger
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Enables the internal PHP debugger support. This feature is still in an experimental state. See also the Debugger Configuration directives in the configuration file.
--enable-discard-path
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If this is enabled, the PHP CGI binary can safely be placed outside of the web tree and people will not be able to circumvent .htaccess security. Read the section in the security chapter about this option.
--enable-bcmath
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Enables bc style arbitrary precision math functions. See also the bcmath.scale option in the configuration file.
--enable-force-cgi-redirect
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Enable the security check for internal server redirects. You should use this if you are running the CGI version with Apache.
When using PHP as a CGI binary, PHP by default always first checks that it is used by redirection (for example under Apache, by using Action directives). This makes sure that the PHP binary cannot be used to bypass standard web server authentication procedures by calling it directly, like http://my.host/cgi-bin/php/secret/doc.html. This example accesses http://my.host/secret/doc.html but does not honour any security settings enforced by httpd for directory /secret.
Not enabling option disables the check and enables bypassing httpd security and authentication settings. Do this only if your server software is unable to indicate that a safe redirection was done and all your files under your document root and user directories may be accessed by anyone.
Read the section in the security chapter about this option.
--disable-short-tags
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Disables the short form <? ?> PHP tags. You must disable the short form if you want to use PHP with XML. With short tags disabled, the only PHP code tag is <?php ?>. This option only sets the default, it may be enabled or disabled with the short_open_tag directive in the configuration file later.
--enable-url-includes
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Makes it possible to run code on other HTTP or FTP servers directly from PHP with include(). See also the include_path option in the configuration file.
To make the PHP installation look for header or library files in different directories, modify the CPPFLAGS and LDFLAGS environment variables, respectively. If you are using a sensible shell, you should be able to do LDFLAGS=-L/my/lib/dir CPPFLAGS=-I/my/include/dir ./configure
When PHP is configured, you are ready to build the CGI executable or the PHP library. The command make should take care of this. If it fails and you can't figure out why, see the Problems section.
If you have built PHP as a CGI program, you may test your build by typing make test. It is always a good idea to test your build. This way you may catch a problem with PHP on your platform early instead of having to struggle with it later.
If you have built PHP as a CGI program, you may benchmark your build by typing make bench. Note that if safe mode is on by default, the benchmark may not be able to finish if it takes longer then the 30 seconds allowed. This is because the set_time_limit() can not be used in safe mode. Use the max_execution_time configuration setting to control this time for your own scripts. make bench ignores the configuration file.
This install guide will help you install and configure PHP on your Windows 9x/NT webservers. This guide was compiled by Bob Silva. The latest revision can be found at http://www.umesd.k12.or.us/php/win32install.html.
This guide provides installation support for:
Personal Web Server (Newest version recommended)
Internet Information Server 3 or 4
Apache 1.3.x
Omni HTTPd 2.0b1
The following steps should be performed on all installations before the server specific instructions.
Extract the distribution file to a directory of your choice. "C:\PHP\" is a good start.
Copy the file, 'php.ini-dist' to your '%WINDOWS%' directory and rename it to 'php.ini'. Your '%WINDOWS%' directory is typically:
| c:\windows for Windows 95/98 |
| c:\winnt or c:\winnt40 for NT servers |
Edit your 'php.ini' file:
You will need to change the 'extension_dir' setting to point to your php-install-dir, or where you have placed your 'php_*.dll' files. ex: c:\php
If you are using Omni Httpd, do not follow the next step. Set the 'doc_root' to point to your webservers document_root. ex: c:\apache\htdocs or c:\webroot
Choose which modules you would like to load when PHP starts. You can uncomment the: 'extension=php_*.dll' lines to load these modules. Some modules require you to have additional libraries installed on your system for the module to work correctly. The PHP FAQ has more information on where to get supporting libraries. You can also load a module dynamically in your script using: dl("php_*.dll");
On PWS and IIS, you can set the browscap.ini to point to: 'c:\windows\system\inetsrv\browscap.ini' on Windows 95/98 and 'c:\winnt\system32\inetsrv\browscap.ini' on NT Server. Additional information on using the browscap functionality in PHP can be found at this mirror, select the "source" button to see it in action.
The DLLs for PHP extensions are prefixed with 'php_'. This prevents confusion between PHP extensions and their supporting libraries.
The recommended method for configuring these servers is to use the INF file included with the distribution (php_iis_reg.inf). You may want to edit this file and make sure the extensions and PHP install directories match your configuration. Or you can follow the steps below to do it manually.
WARNING: These steps involve working directly with the windows registry. One error here can leave your system in an unstable state. We highly recommend that you back up your registry first. The PHP Development team will not be held responsible if you damage your registry.
Run Regedit.
Navigate to: HKEY_LOCAL_MACHINE /System /CurrentControlSet /Services /W3Svc /Parameters /ScriptMap.
On the edit menu select: New->String Value.
Type in the extension you wish to use for your php scripts. ex: .php
Double click on the new string value and enter the path to php.exe in the value data field. ex: c:\php\php.exe %s %s. The '%s %s' is VERY important, PHP will not work properly without it.
Repeat these steps for each extension you wish to associate with PHP scripts.
Now navigate to: HKEY_CLASSES_ROOT
On the edit menu select: New->Key.
Name the key to the extension you setup in the previous section. ex: .php
Highlight the new key and in the right side pane, double click the "default value" and enter phpfile.
Repeat the last step for each extension you set up in the previous section.
Now create another New->Key under HKEY_CLASSES_ROOT and name it phpfile.
Highlight the new key phpfile and in the right side pane, double click the "default value" and enter PHP Script.
Right click on the phpfile key and select New->Key, name it Shell.
Right click on the Shell key and select New->Key, name it open.
Right click on the open key and select New->Key, name it command.
Highlight the new key command and in the right side pane, double click the "default value" and enter the path to php.exe. ex: c:\php\php.exe -q %1. (don't forget the %1).
Exit Regedit.
PWS and IIS 3 users now have a fully operational system. IIS 3 users can use a nifty tool from Steven Genusa to configure their script maps.
To install PHP on an NT Server running IIS 4, follow these instructions:
In Internet Service Manager (MMC), select the Web site or the starting point directory of an application.
Open the directory's property sheets (by right clicking and selecting properties), and then click the Home Directory, Virtual Directory, or Directory tab.
Click the Configuration button, and then click the App Mappings tab.
Click Add, and in the Executable box, type: c:\path-to-php-dir\php.exe %s %s. You MUST have the %s %s on the end, PHP will not function properly if you fail to do this.
In the Extension box, type the file name extension you want associated with PHP scripts. (You must repeat step 5 and 6 for each extension you want accociated with PHP scripts. (.php and .phtml are common.)
Set up the appropriate security. (This is done in Internet Service Manager), and if your NT Server uses NTFS file system, add execute rights for I_USR_ to the directory that contains php.exe.
You must edit your srm.conf or httpd.conf to configure Apache to work with the PHP CGI binary.
Although there can be a few variations of configuring PHP under Apache, this one is simple enough to be used by the newcomer. Please consult the Apache Docs for further configuration directives.
ScriptAlias /php/ "c:/path-to-php-dir/"
AddType application/x-httpd-php .php
AddType application/x-httpd-php .phtml
Action application/x-httpd-php "/php/php.exe"
To use the source code highlighting feature, simply create a PHP script file and stick this code in: <?php show_source ("original_php_script.php"); ?>. Substitute original_php_script.php with the name of the file you wish to show the source of. (this is only one way of doing it). Note: On Win-Apache all back slashes in a path statement such as: "c:\directory\file.ext", must be converted to forward slashes.
This has got to be the easiest config there is:
Step 1: Install Omni server
Step 2: Right click on the blue OmniHTTPd icon in the system tray and select Properties
Step 3: Click on Web Server Global Settings
Step 4: On the 'External' tab, enter: virtual = .php | actual = c:\path-to-php-dir\php.exe
Step 5: On the Mime tab, enter: virtual = wwwserver/stdcgi | actual = .php
Step 6: Click OK
Repeat steps 2 - 6 for each extension you want to associate with PHP.
Table 2-1. PHP Modules
| php_calendar.dll | Calendar conversion functions |
| php_crypt.dll | Crypt functions |
| php_dbase.dll | DBase functions |
| php_dbm.dll | GDBM emulation via Berkely DB2 library |
| php_filepro.dll | READ ONLY access to filepro databases |
| php_gd.dll | GD Library functions for gif manipulation |
| php_hyperwave.dll | HyperWave functions |
| php_imap4r2.dll | IMAP 4 functions |
| php_ldap.dll | LDAP functions |
| php_msql1.dll | mSQL 1 client |
| php_msql2.dll | mSQL 2 client |
| php_mssql.dll | MSSQL client (requires MSSQL DB-Libraries |
| php3_mysql.dll (Built into PHP 4) | MySQL functions |
| php_nsmail.dll | Netscape mail functions |
| php_oci73.dll | Oracle functions |
| php_snmp.dll | SNMP get and walk functions (NT only!) |
| php_zlib.dll | ZLib functions |
Some problems are more common than others. The most common ones are listed in the PHP FAQ, found at http://www.php.net/FAQ.php
If you think you have found a bug in PHP, please report it. The PHP developers probably don't know about it, and unless you report it, chances are it won't be fixed. You can report bugs using the bug-tracking system at http://www.php.net/bugs.php.
If you are still stuck, someone on the PHP mailing list may be able to help you. You should check out the archive first, in case someone already answered someone else who had the same problem as you. The archives are available from the support page on http://www.php.net/. To subscribe to the PHP mailing list, send an empty mail to php-general-subscribe@lists.php.net. The mailing list address is php-general@lists.php.net.
If you want to get help on the mailing list, please try to be precise and give the necessary details about your environment (which operating system, what PHP version, what web server, if you are running PHP as CGI or a server module, etc.), and preferably enough code to make others able to reproduce and test your problem.
The configuration file (called php3.ini in PHP 3.0, and simply php.ini as of PHP 4.0) is read when PHP starts up. For the server module versions of PHP, this happens only once when the web server is started. For the CGI version, it happens on every invocation.
When using PHP as an Apache module, you can also change the configuration settings using directives in Apache configuration files and .htaccess files.
With PHP 3.0, there are Apache directives that correspond to each configuration setting in the php3.ini name, except the name is prefixed by "php3_".
With PHP 4.0, there are just a few Apache directives that allow you to change the PHP configuration settings.
This sets the value of the specified variable.
This is used to set a Boolean configuration option.
This sets the value of the specified variable. "Admin" configuration settings can only be set from within the main Apache configuration files, and not from .htaccess files.
This is used to set a Boolean configuration option.
You can view the settings of the configuration values in the output of phpinfo(). You can also access the values of individial configuration settings using get_cfg_var().
Enables the use of ASP-like <% %> tags in addition to the usual <?php ?> tags. This includes the variable-value printing shorthand of <%= $value %>. For more information, see Escaping from HTML.
Note: Support for ASP-style tags was added in 3.0.4.
Specifies the name of a file that is automatically parsed after the main file. The file is included as if it was called with the include() function, so include_path is used.
The special value none disables auto-appending.
Note: If the script is terminated with exit(), auto-append will not occur.
Specifies the name of a file that is automatically parsed before the main file. The file is included as if it was called with the include() function, so include_path is used.
The special value none disables auto-prepending.
This determines whether errors should be printed to the screen as part of the HTML output or not.
PHP's "root directory" on the server. Only used if non-empty. If PHP is configured with safe mode, no files outside this directory are served.
This directive is really only useful in the Apache module version of PHP. It is used by sites that would like to turn PHP parsing on and off on a per-directory or per-virtual server basis. By putting engine off in the appropriate places in the httpd.conf file, PHP can be enabled or disabled.
Name of file where script errors should be logged. If the special value syslog is used, the errors are sent to the system logger instead. On UNIX, this means syslog(3) and on Windows NT it means the event log. The system logger is not supported on Windows 95.
Set the error reporting level. The parameter is an integer representing a bit field. Add the values of the error reporting levels you want.
Table 3-1. Error Reporting Levels
| bit value | enabled reporting |
|---|---|
| 1 | normal errors |
| 2 | normal warnings |
| 4 | parser errors |
| 8 | non-critical style-related warnings |
Limit the files that can be opened by PHP to the specified directory-tree.
When a script tries to open a file with, for example, fopen or gzopen, the location of the file is checked. When the file is outside the specified directory-tree, PHP will refuse to open it. All symbolic links are resolved, so it's not possible to avoid this restriction with a symlink.
The special value . indicates that the directory in which the script is stored will be used as base-directory.
Under Windows, separate the directories with a semicolon. On all other systems, separate the directories with a colon. As an Apache module, open_basedir paths from parent directories are now automatically inherited.
Note: Support for multiple directories was added in 3.0.7.
The default is to allow all files to be opened.
Set the order of GET/POST/COOKIE variable parsing. The default setting of this directive is "GPC". Setting this to "GP", for example, will cause PHP to completely ignore cookies and to overwrite any GET method variables with POST-method variables of the same name.
On by default. If changed to Off scripts will be terminated as soon as they try to output something after a client has aborted their connection. ignore_user_abort().
Specifies a list of directories where the require(), include() and fopen_with_path() functions look for files. The format is like the system's PATH environment variable: a list of directories separated with a colon in UNIX or semicolon in Windows.
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Example 3-1. UNIX include_path
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Example 3-2. Windows include_path
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Tells whether script error messages should be logged to the server's error log. This option is thus server-specific.
Sets the magic_quotes state for GPC (Get/Post/Cookie) operations. When magic_quotes are on, all ' (single-quote), " (double quote), \ (backslash) and NUL's are escaped with a backslash automatically. If magic_quotes_sybase is also on, a single-quote is escaped with a single-quote instead of a backslash.
If magic_quotes_runtime is enabled, most functions that return data from any sort of external source including databases and text files will have quotes escaped with a backslash. If magic_quotes_sybase is also on, a single-quote is escaped with a single-quote instead of a backslash.
If magic_quotes_sybase is also on, a single-quote is escaped with a single-quote instead of a backslash if magic_quotes_gpc or magic_quotes_runtime is enabled.
This sets the maximum time in seconds a script is allowed to take before it is terminated by the parser. This helps prevent poorly written scripts from tieing up the server.
This sets the maximum amount of memory in bytes that a script is allowed to allocate. This helps prevent poorly written scripts for eating up all available memory on a server.
Tells whether the short form (<? ?>of PHP's open tag should be allowed. If you want to use PHP in combination with XML, you have to disable this option. If disabled, you must use the long form of the open tag (<?php ?>).
If enabled, the last error message will always be present in the global variable $php_errormsg.
If enabled, GET, POST and cookie input can be found in the global associative arrays $HTTP_GET_VARS, $HTTP_POST_VARS and $HTTP_COOKIE_VARS, respectively.
The temporary directory used for storing files when doing file upload. Must be writable by whatever user PHP is running as.
The base name of the directory used on a user's home directory for PHP files, for example public_html.
If enabled, this option makes PHP output a warning when the plus (+) operator is used on strings. This is to make it easier to find scripts that need to be rewritten to using the string concatenator instead (.).
DNS name or IP address of the SMTP server PHP under Windows should use for mail sent with the mail() function.
Which "From:" mail address should be used in mail sent from PHP under Windows.
Where the sendmail program can be found, usually /usr/sbin/sendmail or /usr/lib/sendmail configure does an honest attempt of locating this one for you and set a default, but if it fails, you can set it here.
Systems not using sendmail should set this directive to the sendmail wrapper/replacement their mail system offers, if any. For example, Qmail users can normally set it to /var/qmail/bin/sendmail.
Whether to enable PHP's safe mode. Read the Security chapter for more more information.
If PHP is used in safe mode, system() and the other functions executing system programs refuse to start programs that are not in this directory.
DNS name or IP address of host used by the debugger.
Port number used by the debugger.
Whether the debugger is enabled.
This directive is really only useful in the Apache module version of PHP. You can turn dynamic loading of PHP extensions with dl() on and off per virtual server or per directory.
The main reason for turning dynamic loading off is security. With dynamic loading, it's possible to ignore all the safe_mode and open_basedir restrictions.
The default is to allow dynamic loading, except when using safe-mode. In safe-mode, it's always imposible to use dl().
In what directory PHP should look for dynamically loadable extensions.
Which dynamically loadable extensions to load when PHP starts up.
Whether to allow persistent MySQL connections.
The default server host to use when connecting to the database server if no other host is specified.
The default user name to use when connecting to the database server if no other name is specified.
The default password to use when connecting to the database server if no other password is specified.
The maximum number of persistent MySQL connections per process.
The maximum number of MySQL connections per process, including persistent connections.
Whether to allow persistent mSQL connections.
The maximum number of persistent mSQL connections per process.
The maximum number of mSQL connections per process, including persistent connections.
Whether to allow persistent Postgres connections.
The maximum number of persistent Postgres connections per process.
The maximum number of Postgres connections per process, including persistent connections.
Whether to allow persistent Sybase connections.
The maximum number of persistent Sybase connections per process.
The maximum number of Sybase connections per process, including persistent connections.
Whether to allow persistent Sybase-CT connections. The default is on.
The maximum number of persistent Sybase-CT connections per process. The default is -1 meaning unlimited.
The maximum number of Sybase-CT connections per process, including persistent connections. The default is -1 meaning unlimited.
Server messages with severity greater than or equal to sybct.min_server_severity will be reported as warnings. This value can also be set from a script by calling sybase_min_server_severity(). The default is 10 which reports errors of information severity or greater.
Client library messages with severity greater than or equal to sybct.min_client_severity will be reported as warnings. This value can also be set from a script by calling sybase_min_client_severity(). The default is 10 which effectively disables reporting.
The maximum time in seconds to wait for a connection attempt to succeed before returning failure. Note that if max_execution_time has been exceeded when a connection attempt times out, your script will be terminated before it can take action on failure. The default is one minute.
The maximum time in seconds to wait for a select_db or query operation to succeed before returning failure. Note that if max_execution_time has been exceeded when am operation times out, your script will be terminated before it can take action on failure. The default is no limit.
The name of the host you claim to be connecting from, for display by sp_who. The default is none.
Whether to allow persistent Informix connections.
The maximum number of persistent Informix connections per process.
The maximum number of Informix connections per process, including persistent connections.
The default host to connect to when no host is specified in ifx_connect() or ifx_pconnect().
The default user id to use when none is specified in ifx_connect() or ifx_pconnect().
The default password to use when none is specified in ifx_connect() or ifx_pconnect().
Set to true if you want to return blob columns in a file, false if you want them in memory. You can override the setting at runtime with ifx_blobinfile_mode().
Set to true if you want to return TEXT columns as normal strings in select statements, false if you want to use blob id parameters. You can override the setting at runtime with ifx_textasvarchar().
Set to true if you want to return BYTE columns as normal strings in select queries, false if you want to use blob id parameters. You can override the setting at runtime with ifx_textasvarchar().
Set to true if you want to trim trailing spaces from CHAR columns when fetching them.
Set to true if you want to return NULL columns as the literal string "NULL", false if you want them returned as the empty string "". You can override this setting at runtime with ifx_nullformat().
Number of decimal digits for all bcmath functions.
Name of browser capabilities file. See also get_browser().
ODBC data source to use if none is specified in odbc_connect() or odbc_pconnect().
User name to use if none is specified in odbc_connect() or odbc_pconnect().
Password to use if none is specified in odbc_connect() or odbc_pconnect().
Whether to allow persistent ODBC connections.
The maximum number of persistent ODBC connections per process.
The maximum number of ODBC connections per process, including persistent connections.
PHP is a powerful language and the interpreter, whether included in a web server as a module or executed as a separate CGI binary, is able to access files, execute commands and open network connections on the server. These properties make anything run on a web server insecure by default. PHP is designed specifically to be a more secure language for writing CGI programs than Perl or C, and with correct selection of compile-time and runtime configuration options it gives you exactly the combination of freedom and security you need.
As there are many different ways of utilizing PHP, there are many configuration options controlling its behaviour. A large selection of options guarantees you can use PHP for a lot of purposes, but it also means there are combinations of these options and server configurations that result in an insecure setup. This chapter explains the different configuration option combinations and the situations they can be safely used.
Using PHP as a CGI binary is an option for setups that for some reason do not wish to integrate PHP as a module into server software (like Apache), or will use PHP with different kinds of CGI wrappers to create safe chroot and setuid environments for scripts. This setup usually involves installing executable PHP binary to the web server cgi-bin directory. CERT advisory CA-96.11 recommends against placing any interpreters into cgi-bin. Even if the PHP binary can be used as a standalone interpreter, PHP is designed to prevent the attacks this setup makes possible:
Accessing system files: http://my.host/cgi-bin/php?/etc/passwd
The query information in a url after the question mark (?) is passed as command line arguments to the interpreter by the CGI interface. Usually interpreters open and execute the file specified as the first argument on the command line.
When invoked as a CGI binary, PHP refuses to interpret the command line arguments.
Accessing any web document on server: http://my.host/cgi-bin/php/secret/doc.html
The path information part of the url after the PHP binary name, /secret/doc.html is conventionally used to specify the name of the file to be opened and interpreted by the CGI program. Usually some web server configuration directives (Apache: Action) are used to redirect requests to documents like http://my.host/secret/script.php3 to the PHP interpreter. With this setup, the web server first checks the access permissions to the directory /secret, and after that creates the redirected request http://my.host/cgi-bin/php/secret/script.php3. Unfortunately, if the request is originally given in this form, no access checks are made by web server for file /secret/script.php3, but only for the /cgi-bin/php file. This way any user able to access /cgi-bin/php is able to access any protected document on the web server.
In PHP, compile-time configuration option --enable-force-cgi-redirect and runtime configuration directives doc_root and user_dir can be used to prevent this attack, if the server document tree has any directories with access restrictions. See below for full the explanation of the different combinations.
If your server does not have any content that is not restricted by password or ip based access control, there is no need for these configuration options. If your web server does not allow you to do redirects, or the server does not have a way to communicate to the PHP binary that the request is a safely redirected request, you can specify the option --disable-force-cgi-redirect to the configure script. You still have to make sure your PHP scripts do not rely on one or another way of calling the script, neither by directly http://my.host/cgi-bin/php/dir/script.php3 nor by redirection http://my.host/dir/script.php3.
Redirection can be configured in Apache by using AddHandler and Action directives (see below).
This compile-time option prevents anyone from calling PHP directly with a url like http://my.host/cgi-bin/php/secretdir/script.php3. Instead, PHP will only parse in this mode if it has gone through a web server redirect rule.
Usually the redirection in the Apache configuration is done with the following directives:
Action php3-script /cgi-bin/php
AddHandler php3-script .php3
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This option has only been tested with the Apache web server, and relies on Apache to set the non-standard CGI environment variable REDIRECT_STATUS on redirected requests. If your web server does not support any way of telling if the request is direct or redirected, you cannot use this option and you must use one of the other ways of running the CGI version documented here.
To include active content, like scripts and executables, in the web server document directories is sometimes consider an insecure practice. If, because of some configuration mistake, the scripts are not executed but displayed as regular HTML documents, this may result in leakage of intellectual property or security information like passwords. Therefore many sysadmins will prefer setting up another directory structure for scripts that are accessible only through the PHP CGI, and therefore always interpreted and not displayed as such.
Also if the method for making sure the requests are not redirected, as described in the previous section, is not available, it is necessary to set up a script doc_root that is different from web document root.
You can set the PHP script document root by the configuration directive doc_root in the configuration file, or you can set the environment variable PHP_DOCUMENT_ROOT. If it is set, the CGI version of PHP will always construct the file name to open with this doc_root and the path information in the request, so you can be sure no script is executed outside this directory (except for user_dir below).
Another option usable here is user_dir. When user_dir is unset, only thing controlling the opened file name is doc_root. Opening an url like http://my.host/~user/doc.php3 does not result in opening a file under users home directory, but a file called ~user/doc.php3 under doc_root (yes, a directory name starting with a tilde [~]).
If user_dir is set to for example public_php, a request like http://my.host/~user/doc.php3 will open a file called doc.php3 under the directory named public_php under the home directory of the user. If the home of the user is /home/user, the file executed is /home/user/public_php/doc.php3.
user_dir expansion happens regardless of the doc_root setting, so you can control the document root and user directory access separately.
A very secure option is to put the PHP parser binary somewhere outside of the web tree of files. In /usr/local/bin, for example. The only real downside to this option is that you will now have to put a line similar to:
#!/usr/local/bin/php
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To get PHP to handle PATH_INFO and PATH_TRANSLATED information correctly with this setup, the php parser should be compiled with the --enable-discard-path configure option.
When PHP is used as an Apache module it inherits Apache's user permissions (typically those of the "nobody" user).
There are four ways of escaping from HTML and entering "PHP code mode":
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Example 5-1. Ways of escaping from HTML
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The first way is only available if short tags have been enabled. This can be done via the short_tags() function, by enabling the short_open_tag configuration setting in the PHP config file, or by compiling PHP with the --enable-short-tags option to configure.
The fourth way is only available if ASP-style tags have been enabled using the asp_tags configuration setting.
Note: Support for ASP-style tags was added in 3.0.4.
The closing tag for the block will include the immediately trailing newline if one is present.
Instructions are separated the same as in C or perl - terminate each statement with a semicolon.
The closing tag (?>) also implies the end of the statement, so the following are equivalent:
<?php
echo "This is a test";
?>
<?php echo "This is a test" ?>
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PHP supports 'C', 'C++' and Unix shell-style comments. For example:
<?php
echo "This is a test"; // This is a one-line c++ style comment
/* This is a multi line comment
yet another line of comment */
echo "This is yet another test";
echo "One Final Test"; # This is shell-style style comment
?>
|
The "one-line" comment styles actually only comment to the end of the line or the current block of PHP code, whichever comes first.
<h1>This is an <?# echo "simple";?> example.</h1> <p>The header above will say 'This is an example'. |
You should be careful not to nest 'C' style comments, which can happen when commenting out large blocks.
<?php
/*
echo "This is a test"; /* This comment will cause a problem */
*/
?>
|
PHP supports the following types:
The type of a variable is usually not set by the programmer; rather, it is decided at runtime by PHP depending on the context in which that variable is used.
If you would like to force a variable to be converted to a certain type, you may either cast the variable or use the settype() function on it.
Note that a variable may behave in different manners in certain situations, depending on what type it is at the time. For more information, see the section on Type Juggling.
Integers can be specified using any of the following syntaxes:
$a = 1234; # decimal number
$a = -123; # a negative number
$a = 0123; # octal number (equivalent to 83 decimal)
$a = 0x12; # hexadecimal number (equivalent to 18 decimal)
|
Floating point numbers ("doubles") can be specified using any of the following syntaxes:
$a = 1.234; $a = 1.2e3;
|
| Warning |
|
It is quite usual that simple decimal fractions like 0.1 or 0.7 cannot be converted into their internal binary counterparts without a little loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8 as the result of the internal representation really being something like 7.9999999999.... This is related to the fact that it is impossible to exactly express some fractions in decimal notation with a finite number of digits. For instance, 1/3 in decimal form becomes 0.3333333. . .. So never trust floating number results to the last digit and never compare floating point numbers for equality. If you really need higher precision, you should use the arbitrary precision math functions instead. |
Strings can be specified using one of two sets of delimiters.
If the string is enclosed in double-quotes ("), variables within the string will be expanded (subject to some parsing limitations). As in C and Perl, the backslash ("\") character can be used in specifying special characters:
Table 6-1. Escaped characters
| sequence | meaning |
|---|---|
| \n | linefeed (LF or 0x0A in ASCII) |
| \r | carriage return (CR or 0x0D in ASCII) |
| \t | horizontal tab (HT or 0x09 in ASCII) |
| \\ | backslash |
| \$ | dollar sign |
| \" | double-quote |
| \[0-7]{1,3} | the sequence of characters matching the regular expression is a character in octal notation |
| \x[0-9A-Fa-f]{1,2} | the sequence of characters matching the regular expression is a character in hexadecimal notation |
You can escape any other character, but a warning will be issued at the highest warning level.
The second way to delimit a string uses the single-quote ("'") character. When a string is enclosed in single quotes, the only escapes that will be understood are "\\" and "\'". This is for convenience, so that you can have single-quotes and backslashes in a single-quoted string. Variables will not be expanded inside a single-quoted string.
Another way to delimit strings is by using here doc syntax ("<<<"). One should provide an identifier after <<<, then the string, and then the same identifier to close the quotation. The closing identifier must begin in the first column of the line.
Here doc text behaves just like a double-quoted string, without the double-quotes. This means that you do not need to escape quotes in your here docs, but you can still use the escape codes listed above. Variables are expanded, but the same care must be taken when expressing complex variables inside a here doc as with strings.
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Example 6-1. Here doc string quoting example
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Note: Here doc support was added in PHP 4.
Strings may be concatenated using the '.' (dot) operator. Note that the '+' (addition) operator will not work for this. Please see String operators for more information.
Characters within strings may be accessed by treating the string as a numerically-indexed array of characters, using C-like syntax. See below for examples.
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Example 6-2. Some string examples
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When a string is evaluated as a numeric value, the resulting value and type are determined as follows.
The string will evaluate as a double if it contains any of the characters '.', 'e', or 'E'. Otherwise, it will evaluate as an integer.
The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used. Otherwise, the value will be 0 (zero). Valid numeric data is an optional sign, followed by one or more digits (optionally containing a decimal point), followed by an optional exponent. The exponent is an 'e' or 'E' followed by one or more digits.
When the first expression is a string, the type of the variable will depend on the second expression.
$foo = 1 + "10.5"; // $foo is double (11.5)
$foo = 1 + "-1.3e3"; // $foo is double (-1299)
$foo = 1 + "bob-1.3e3"; // $foo is integer (1)
$foo = 1 + "bob3"; // $foo is integer (1)
$foo = 1 + "10 Small Pigs"; // $foo is integer (11)
$foo = 1 + "10 Little Piggies"; // $foo is integer (11)
$foo = "10.0 pigs " + 1; // $foo is integer (11)
$foo = "10.0 pigs " + 1.0; // $foo is double (11)
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For more information on this conversion, see the Unix manual page for strtod(3).
If you would like to test any of the examples in this section, you can cut and paste the examples and insert the following line to see for yourself what's going on:
echo "\$foo==$foo; type is " . gettype ($foo) . "<br>\n";
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Arrays actually act like both hash tables (associative arrays) and indexed arrays (vectors).
PHP supports both scalar and associative arrays. In fact, there is no difference between the two. You can create an array using the list() or array() functions, or you can explicitly set each array element value.
$a[0] = "abc";
$a[1] = "def";
$b["foo"] = 13;
|
You can also create an array by simply adding values to the array. When you assign a value to an array variable using empty brackets, the value will be added onto the end of the array.
$a[] = "hello"; // $a[2] == "hello"
$a[] = "world"; // $a[3] == "world"
|
Arrays may be sorted using the asort(), arsort(), ksort(), rsort(), sort(), uasort(), usort(), and uksort() functions depending on the type of sort you want.
You can count the number of items in an array using the count() function.
You can traverse an array using next() and prev() functions. Another common way to traverse an array is to use the each() function.
Multi-dimensional arrays are actually pretty simple. For each dimension of the array, you add another [key] value to the end:
$a[1] = $f; # one dimensional examples
$a["foo"] = $f;
$a[1][0] = $f; # two dimensional
$a["foo"][2] = $f; # (you can mix numeric and associative indices)
$a[3]["bar"] = $f; # (you can mix numeric and associative indices)
$a["foo"][4]["bar"][0] = $f; # four dimensional!
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In PHP3 it is not possible to reference multidimensional arrays directly within strings. For instance, the following will not have the desired result:
$a[3]['bar'] = 'Bob';
echo "This won't work: $a[3][bar]";
|
$a[3]['bar'] = 'Bob';
echo "This will work: " . $a[3][bar];
|
In PHP4, however, the whole problem may be circumvented by enclosing the array reference (inside the string) in curly braces:
$a[3]['bar'] = 'Bob';
echo "This will work: {$a[3][bar]}";
|
You can "fill up" multi-dimensional arrays in many ways, but the trickiest one to understand is how to use the array() command for associative arrays. These two snippets of code fill up the one-dimensional array in the same way:
# Example 1:
$a["color"] = "red";
$a["taste"] = "sweet";
$a["shape"] = "round";
$a["name"] = "apple";
$a[3] = 4;
# Example 2:
$a = array(
"color" => "red",
"taste" => "sweet",
"shape" => "round",
"name" => "apple",
3 => 4
);
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The array() function can be nested for multi-dimensional arrays:
<?
$a = array(
"apple" => array(
"color" => "red",
"taste" => "sweet",
"shape" => "round"
),
"orange" => array(
"color" => "orange",
"taste" => "tart",
"shape" => "round"
),
"banana" => array(
"color" => "yellow",
"taste" => "paste-y",
"shape" => "banana-shaped"
)
);
echo $a["apple"]["taste"]; # will output "sweet"
?>
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To initialize an object, you use the new statement to instantiate the object to a variable.
<?php
class foo {
function do_foo() {
echo "Doing foo.";
}
}
$bar = new foo;
$bar->do_foo();
?>
|
For a full discussion, please read the section Classes and Objects.
PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which that variable is used. That is to say, if you assign a string value to variable var, var becomes a string. If you then assign an integer value to var, it becomes an integer.
An example of PHP's automatic type conversion is the addition operator '+'. If any of the operands is a double, then all operands are evaluated as doubles, and the result will be a double. Otherwise, the operands will be interpreted as integers, and the result will also be an integer. Note that this does NOT change the types of the operands themselves; the only change is in how the operands are evaluated.
$foo = "0"; // $foo is string (ASCII 48)
$foo++; // $foo is the string "1" (ASCII 49)
$foo += 1; // $foo is now an integer (2)
$foo = $foo + 1.3; // $foo is now a double (3.3)
$foo = 5 + "10 Little Piggies"; // $foo is integer (15)
$foo = 5 + "10 Small Pigs"; // $foo is integer (15)
|
If the last two examples above seem odd, see String conversion.
If you wish to force a variable to be evaluated as a certain type, see the section on Type casting. If you wish to change the type of a variable, see settype().
If you would like to test any of the examples in this section, you can cut and paste the examples and insert the following line to see for yourself what's going on:
echo "\$foo==$foo; type is " . gettype ($foo) . "<br>\n";
|
Note: The behaviour of an automatic conversion to array is currently undefined.
$a = 1; // $a is an integer $a[0] = "f"; // $a becomes an array, with $a[0] holding "f"While the above example may seem like it should clearly result in $a becoming an array, the first element of which is 'f', consider this:
$a = "1"; // $a is a string $a[0] = "f"; // What about string offsets? What happens?Since PHP supports indexing into strings via offsets using the same syntax as array indexing, the example above leads to a problem: should $a become an array with its first element being "f", or should "f" become the first character of the string $a?
For this reason, as of PHP 3.0.12 and PHP 4.0b3-RC4, the result of this automatic conversion is considered to be undefined. Fixes are, however, being discussed.
Type casting in PHP works much as it does in C: the name of the desired type is written in parentheses before the variable which is to be cast.
$foo = 10; // $foo is an integer
$bar = (double) $foo; // $bar is a double
|
The casts allowed are:
(int), (integer) - cast to integer
(real), (double), (float) - cast to double
(string) - cast to string
(array) - cast to array
(object) - cast to object
Note that tabs and spaces are allowed inside the parentheses, so the following are functionally equivalent:
$foo = (int) $bar;
$foo = ( int ) $bar;
|
It may not be obvious exactly what will happen when casting between certain types. For instance, the following should be noted.
When casting from a scalar or a string variable to an array, the variable will become the first element of the array:
$var = 'ciao';
$arr = (array) $var;
echo $arr[0]; // outputs 'ciao'
|
When casting from a scalar or a string variable to an object, the variable will become an attribute of the object; the attribute name will be 'scalar':
$var = 'ciao';
$obj = (object) $var;
echo $obj->scalar; // outputs 'ciao'
|
Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive.
Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: '[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*'
Note: For our purposes here, a letter is a-z, A-Z, and the ASCII characters from 127 through 255 (0x7f-0xff).
$var = "Bob";
$Var = "Joe";
echo "$var, $Var"; // outputs "Bob, Joe"
$4site = 'not yet'; // invalid; starts with a number
$_4site = 'not yet'; // valid; starts with an underscore
$tδyte = 'mansikka'; // valid; 'δ' is ASCII 228.
|
In PHP3, variables are always assigned by value. That is to say, when you assign an expression to a variable, the entire value of the original expression is copied into the destination variable. This means, for instance, that after assigning one variable's value to another, changing one of those variables will have no effect on the other. For more information on this kind of assignment, see Expressions.
PHP4 offers another way to assign values to variables: assign by reference. This means that the new variable simply references (in other words, "becomes an alias for" or "points to") the original variable. Changes to the new variable affect the original, and vice versa. This also means that no copying is performed; thus, the assignment happens more quickly. However, any speedup will likely be noticed only in tight loops or when assigning large arrays or objects.
To assign by reference, simply prepend an ampersand (&) to the beginning of the variable which is being assigned (the source variable). For instance, the following code snippet outputs 'My name is Bob' twice:
<?php
$foo = 'Bob'; // Assign the value 'Bob' to $foo
$bar = &$foo; // Reference $foo via $bar.
$bar = "My name is $bar"; // Alter $bar...
echo $foo; // $foo is altered too.
echo $bar;
?>
|
One important thing to note is that only named variables may be assigned by reference.
<?php
$foo = 25;
$bar = &$foo; // This is a valid assignment.
$bar = &(24 * 7); // Invalid; references an unnamed expression.
function test() {
return 25;
}
$bar = &test(); // Invalid.
?>
|
PHP provides a large number of predefined variables to any script which it runs. Many of these variables, however, cannot be fully documented as they are dependent upon which server is running, the version and setup of the server, and other factors. Some of these variables will not be available when PHP is run on the command-line.
Despite these factors, here is a list of predefined variables available under a stock installation of PHP 3 running as a module under a stock installation of Apache 1.3.6.
For a list of all predefined variables (and lots of other useful information), please see (and use) phpinfo().
Note: This list is neither exhaustive nor intended to be. It is simply a guideline as to what sorts of predefined variables you can expect to have access to in your script.
These variables are created by the Apache webserver. If you are running another webserver, there is no guarantee that it will provide the same variables; it may omit some, or provide others not listed here. That said, a large number of these variables are accounted for in the CGI 1.1 specification, so you should be able to expect those.
Note that few, if any, of these will be available (or indeed have any meaning) if running PHP on the command line.
What revision of the CGI specification the server is using; i.e. 'CGI/1.1'.
The name of the server host under which the current script is executing. If the script is running on a virtual host, this will be the value defined for that virtual host.
Server identification string, given in the headers when responding to requests.
Name and revision of the information protocol via which the page was requested; i.e. 'HTTP/1.0';
Which request method was used to access the page; i.e. 'GET', 'HEAD', 'POST', 'PUT'.
The query string, if any, via which the page was accessed.
The document root directory under which the current script is executing, as defined in the server's configuration file.
Contents of the Accept: header from the current request, if there is one.
Contents of the Accept-Charset: header from the current request, if there is one. Example: 'iso-8859-1,*,utf-8'.
Contents of the Accept-Encoding: header from the current request, if there is one. Example: 'gzip'.
Contents of the Accept-Language: header from the current request, if there is one. Example: 'en'.
Contents of the Connection: header from the current request, if there is one. Example: 'Keep-Alive'.
Contents of the Host: header from the current request, if there is one.
The address of the page (if any) which referred the browser to the current page. This is set by the user's browser; not all browsers will set this.
Contents of the User_Agent: header from the current request, if there is one. This is a string denoting the browser software being used to view the current page; i.e. Mozilla/4.5 [en] (X11; U; Linux 2.2.9 i586). Among other things, you can use this value with get_browser() to tailor your page's functionality to the capabilities of the user's browser.
The IP address from which the user is viewing the current page.
The port being used on the user's machine to communicate with the web server.
The absolute pathname of the currently executing script.
The value given to the SERVER_ADMIN (for Apache) directive in the web server configuration file. If the script is running on a virtual host, this will be the value defined for that virtual host.
The port on the server machine being used by the web server for communication. For default setups, this will be '80'; using SSL, for instance, will change this to whatever your defined secure HTTP port is.
String containing the server version and virtual host name which are added to server-generated pages, if enabled.
Filesystem- (not document root-) based path to the current script, after the server has done any virtual-to-real mapping.
Contains the current script's path. This is useful for pages which need to point to themselves.
The URI which was given in order to access this page; for instance, '/index.html'.
These variables are imported into PHP's global namespace from the environment under which the PHP parser is running. Many are provided by the shell under which PHP is running and different systems are likely running different kinds of shells, a definitive list is impossible. Please see your shell's documentation for a list of defined environment variables.
Other environment variables include the CGI variables, placed there regardless of whether PHP is running as a server module or CGI processor.
These variables are created by PHP itself.
Array of arguments passed to the script. When the script is run on the command line, this gives C-style access to the command line parameters. When called via the GET method, this will contain the query string.
Contains the number of command line parameters passed to the script (if run on the command line).
The filename of the currently executing script, relative to the document root. If PHP is running as a command-line processor, this variable is not available.
An associative array of variables passed to the current script via HTTP cookies. Only available if variable tracking has been turned on via either the track_vars configuration directive or the <?php_track_vars?> directive.
An associative array of variables passed to the current script via the HTTP GET method. Only available if variable tracking has been turned on via either the track_vars configuration directive or the <?php_track_vars?> directive.
An associative array of variables passed to the current script via the HTTP POST method. Only available if variable tracking has been turned on via either the track_vars configuration directive or the <?php_track_vars?> directive.
The scope of a variable is the context within which it is defined. For the most part all PHP variables only have a single scope. This single scope spans included and required files as well. For example:
$a = 1;
include "b.inc";
|
Here the $a variable will be available within the included b.inc script. However, within user-defined functions a local function scope is introduced. Any variable used inside a function is by default limited to the local function scope. For example:
$a = 1; /* global scope */
Function Test () {
echo $a; /* reference to local scope variable */
}
Test ();
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This script will not produce any output because the echo statement refers to a local version of the $a variable, and it has not been assigned a value within this scope. You may notice that this is a little bit different from the C language in that global variables in C are automatically available to functions unless specifically overridden by a local definition. This can cause some problems in that people may inadvertently change a global variable. In PHP global variables must be declared global inside a function if they are going to be used in that function. An example:
$a = 1;
$b = 2;
Function Sum () {
global $a, $b;
$b = $a + $b;
}
Sum ();
echo $b;
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The above script will output "3". By declaring $a and $b global within the function, all references to either variable will refer to the global version. There is no limit to the number of global variables that can be manipulated by a function.
A second way to access variables from the global scope is to use the special PHP-defined $GLOBALS array. The previous example can be rewritten as:
$a = 1;
$b = 2;
Function Sum () {
$GLOBALS["b"] = $GLOBALS["a"] + $GLOBALS["b"];
}
Sum ();
echo $b;
|
The $GLOBALS array is an associative array with the name of the global variable being the key and the contents of that variable being the value of the array element.
Another important feature of variable scoping is the static variable. A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope. Consider the following example:
Function Test () {
$a = 0;
echo $a;
$a++;
}
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This function is quite useless since every time it is called it sets $a to 0 and prints "0". The $a++ which increments the variable serves no purpose since as soon as the function exits the $a variable disappears. To make a useful counting function which will not lose track of the current count, the $a variable is declared static:
Function Test () {
static $a = 0;
echo $a;
$a++;
}
|
Now, every time the Test() function is called it will print the value of $a and increment it.
Static variables also provide one way to deal with recursive functions. A recursive function is one which calls itself. Care must be taken when writing a recursive function because it is possible to make it recurse indefinitely. You must make sure you have an adequate way of terminating the recursion. The following simple function recursively counts to 10, using the static variable $count to know when to stop:
Function Test () {
static $count = 0;
$count++;
echo $count;
if ($count < 10) {
Test ();
}
$count--;
}
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Sometimes it is convenient to be able to have variable variable names. That is, a variable name which can be set and used dynamically. A normal variable is set with a statement such as:
$a = "hello";
|
A variable variable takes the value of a variable and treats that as the name of a variable. In the above example, hello, can be used as the name of a variable by using two dollar signs. i.e.
$$a = "world";
|
At this point two variables have been defined and stored in the PHP symbol tree: $a with contents "hello" and $hello with contents "world". Therefore, this statement:
echo "$a ${$a}";
|
produces the exact same output as:
echo "$a $hello";
|
i.e. they both produce: hello world.
In order to use variable variables with arrays, you have to resolve an ambiguity problem. That is, if you write $$a[1] then the parser needs to know if you meant to use $a[1] as a variable, or if you wanted $$a as the variable and then the [1] index from that variable. The syntax for resolving this ambiguity is: ${$a[1]} for the first case and ${$a}[1] for the second.
When a form is submitted to a PHP script, any variables from that form will be automatically made available to the script by PHP. For instance, consider the following form:
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Example 7-1. Simple form variable
|
When submitted, PHP will create the variable $name, which will will contain whatever what entered into the Name: field on the form.
PHP also understands arrays in the context of form variables, but only in one dimension. You may, for example, group related variables together, or use this feature to retrieve values from a multiple select input:
|
Example 7-2. More complex form variables
|
If PHP's track_vars feature is turned on, either by the track_vars configuration setting or the <?php_track_vars?> directive, then variables submitted via the POST or GET methods will also be found in the global associative arrays $HTTP_POST_VARS and $HTTP_GET_VARS as appropriate.
When submitting a form, it is possible to use an image instead of the standard submit button with a tag like:
<input type=image src="image.gif" name="sub">
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When the user clicks somewhere on the image, the accompanying form will be transmitted to the server with two additional variables, sub_x and sub_y. These contain the coordinates of the user click within the image. The experienced may note that the actual variable names sent by the browser contains a period rather than an underscore, but PHP converts the period to an underscore automatically.
PHP transparently supports HTTP cookies as defined by Netscape's Spec. Cookies are a mechanism for storing data in the remote browser and thus tracking or identifying return users. You can set cookies using the SetCookie() function. Cookies are part of the HTTP header, so the SetCookie function must be called before any output is sent to the browser. This is the same restriction as for the Header() function. Any cookies sent to you from the client will automatically be turned into a PHP variable just like GET and POST method data.
If you wish to assign multiple values to a single cookie, just add [] to the cookie name. For example:
SetCookie ("MyCookie[]", "Testing", time()+3600);
|
Note that a cookie will replace a previous cookie by the same name in your browser unless the path or domain is different. So, for a shopping cart application you may want to keep a counter and pass this along. i.e.
|
Example 7-3. SetCookie Example
|
PHP automatically makes environment variables available as normal PHP variables.
echo $HOME; /* Shows the HOME environment variable, if set. */
|
Since information coming in via GET, POST and Cookie mechanisms also automatically create PHP variables, it is sometimes best to explicitly read a variable from the environment in order to make sure that you are getting the right version. The getenv() function can be used for this. You can also set an environment variable with the putenv() function.
Typically, PHP does not alter the names of variables when they are passed into a script. However, it should be noted that the dot (period, full stop) is not a valid character in a PHP variable name. For the reason, look at it:
$varname.ext; /* invalid variable name */
|
For this reason, it is important to note that PHP will automatically replace any dots in incoming variable names with underscores.
Because PHP determines the types of variables and converts them (generally) as needed, it is not always obvious what type a given variable is at any one time. PHP includes several functions which find out what type a variable is. They are gettype(), is_long(), is_double(), is_string(), is_array(), and is_object().
PHP defines several constants and provides a mechanism for defining more at run-time. Constants are much like variables, save for the two facts that constants must be defined using the define() function, and that they cannot later be redefined to another value.
The predefined constants (always available) are:
The name of the script file presently being parsed. If used within a file which has been included or required, then the name of the included file is given, and not the name of the parent file.
The number of the line within the current script file which is being parsed. If used within a file which has been included or required, then the position within the included file is given.
The string representation of the version of the PHP parser presently in use; e.g. '3.0.8-dev'.
The name of the operating system on which the PHP parser is executing; e.g. 'Linux'.
A true value.
A false value.
Denotes an error other than a parsing error from which recovery is not possible.
Denotes a condition where PHP knows something is wrong, but will continue anyway; these can be caught by the script itself. An example would be an invalid regexp in ereg().
The parser choked on invalid syntax in the script file. Recovery is not possible.
Something happened which may or may not be an error. Execution continues. Examples include using an unquoted string as a hash index, or accessing a variable which has not been set.
All of the E_* constants rolled into one. If used with error_reporting(), will cause any and all problems noticed by PHP to be reported.
The E_* constants are typically used with the error_reporting() function for setting the error reporting level. See all these constants at Error handling.
You can define additional constants using the define() function.
Note that these are constants, not C-style macros; only valid scalar data may be represented by a constant.
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Example 8-1. Defining Constants
|
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Example 8-2. Using __FILE__ and __LINE__
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Expressions are the most important building stones of PHP. In PHP, almost anything you write is an expression. The simplest yet most accurate way to define an expression is "anything that has a value".
The most basic forms of expressions are constants and variables. When you type "$a = 5", you're assigning '5' into $a. '5', obviously, has the value 5, or in other words '5' is an expression with the value of 5 (in this case, '5' is an integer constant).
After this assignment, you'd expect $a's value to be 5 as well, so if you wrote $b = $a, you'd expect it to behave just as if you wrote $b = 5. In other words, $a is an expression with the value of 5 as well. If everything works right, this is exactly what will happen.
Slightly more complex examples for expressions are functions. For instance, consider the following function:
function foo () {
return 5;
}
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Assuming you're familiar with the concept of functions (if you're not, take a look at the chapter about functions), you'd assume that typing $c = foo() is essentially just like writing $c = 5, and you're right. Functions are expressions with the value of their return value. Since foo() returns 5, the value of the expression 'foo()' is 5. Usually functions don't just return a static value but compute something.
Of course, values in PHP don't have to be integers, and very often they aren't. PHP supports three scalar value types: integer values, floating point values and string values (scalar values are values that you can't 'break' into smaller pieces, unlike arrays, for instance). PHP also supports two composite (non-scalar) types: arrays and objects. Each of these value types can be assigned into variables or returned from functions.
So far, users of PHP/FI 2 shouldn't feel any change. However, PHP takes expressions much further, in the same way many other languages do. PHP is an expression-oriented language, in the sense that almost everything is an expression. Consider the example we've already dealt with, '$a = 5'. It's easy to see that there are two values involved here, the value of the integer constant '5', and the value of $a which is being updated to 5 as well. But the truth is that there's one additional value involved here, and that's the value of the assignment itself. The assignment itself evaluates to the assigned value, in this case 5. In practice, it means that '$a = 5', regardless of what it does, is an expression with the value 5. Thus, writing something like '$b = ($a = 5)' is like writing '$a = 5; $b = 5;' (a semicolon marks the end of a statement). Since assignments are parsed in a right to left order, you can also write '$b = $a = 5'.
Another good example of expression orientation is pre- and post-increment and decrement. Users of PHP/FI 2 and many other languages may be familiar with the notation of variable++ and variable--. These are increment and decrement operators. In PHP/FI 2, the statement '$a++' has no value (is not an expression), and thus you can't assign it or use it in any way. PHP enhances the increment/decrement capabilities by making these expressions as well, like in C. In PHP, like in C, there are two types of increment - pre-increment and post-increment. Both pre-increment and post-increment essentially increment the variable, and the effect on the variable is idential. The difference is with the value of the increment expression. Pre-increment, which is written '++$variable', evaluates to the incremented value (PHP increments the variable before reading its value, thus the name 'pre-increment'). Post-increment, which is written '$variable++' evaluates to the original value of $variable, before it was incremented (PHP increments the variable after reading its value, thus the name 'post-increment').
A very common type of expressions are comparison expressions. These expressions evaluate to either 0 or 1, meaning FALSE or TRUE (respectively). PHP supports > (bigger than), >= (bigger than or equal to), == (equal), != (not equal), < (smaller than) and <= (smaller than or equal to). These expressions are most commonly used inside conditional execution, such as if statements.
The last example of expressions we'll deal with here is combined operator-assignment expressions. You already know that if you want to increment $a by 1, you can simply write '$a++' or '++$a'. But what if you want to add more than one to it, for instance 3? You could write '$a++' multiple times, but this is obviously not a very efficient or comfortable way. A much more common practice is to write '$a = $a + 3'. '$a + 3' evaluates to the value of $a plus 3, and is assigned back into $a, which results in incrementing $a by 3. In PHP, as in several other languages like C, you can write this in a shorter way, which with time would become clearer and quicker to understand as well. Adding 3 to the current value of $a can be written '$a += 3'. This means exactly "take the value of $a, add 3 to it, and assign it back into $a". In addition to being shorter and clearer, this also results in faster execution. The value of '$a += 3', like the value of a regular assignment, is the assigned value. Notice that it is NOT 3, but the combined value of $a plus 3 (this is the value that's assigned into $a). Any two-place operator can be used in this operator-assignment mode, for example '$a -= 5' (subtract 5 from the value of $a), '$b *= 7' (multiply the value of $b by 7), etc.
There is one more expression that may seem odd if you haven't seen it in other languages, the ternary conditional operator:
$first ? $second : $third |
The following example should help you understand pre- and post-increment and expressions in general a bit better:
function double($i) {
return $i*2;
}
$b = $a = 5; /* assign the value five into the variable $a and $b */
$c = $a++; /* post-increment, assign original value of $a
(5) to $c */
$e = $d = ++$b; /* pre-increment, assign the incremented value of
$b (6) to $d and $e */
/* at this point, both $d and $e are equal to 6 */
$f = double($d++); /* assign twice the value of $d before
the increment, 2*6 = 12 to $f */
$g = double(++$e); /* assign twice the value of $e after
the increment, 2*7 = 14 to $g */
$h = $g += 10; /* first, $g is incremented by 10 and ends with the
value of 24. the value of the assignment (24) is
then assigned into $h, and $h ends with the value
of 24 as well. */
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In the beginning of the chapter we said that we'll be describing the various statement types, and as promised, expressions can be statements. However, not every expression is a statement. In this case, a statement has the form of 'expr' ';' that is, an expression followed by a semicolon. In '$b=$a=5;', $a=5 is a valid expression, but it's not a statement by itself. '$b=$a=5;' however is a valid statement.
One last thing worth mentioning is the truth value of expressions. In many events, mainly in conditional execution and loops, you're not interested in the specific value of the expression, but only care about whether it means TRUE or FALSE (PHP doesn't have a dedicated boolean type). The truth value of expressions in PHP is calculated in a similar way to perl. Any numeric non-zero numeric value is TRUE, zero is FALSE. Be sure to note that negative values are non-zero and are thus considered TRUE! The empty string and the string "0" are FALSE; all other strings are TRUE. With non-scalar values (arrays and objects) - if the value contains no elements it's considered FALSE, otherwise it's considered TRUE.
PHP provides a full and powerful implementation of expressions, and documenting it entirely goes beyond the scope of this manual. The above examples should give you a good idea about what expressions are and how you can construct useful expressions. Throughout the rest of this manual we'll write expr to indicate any valid PHP expression.
Remember basic arithmetic from school? These work just like those.
Table 10-1. Arithmetic Operators
| Example | Name | Result |
|---|---|---|
| $a + $b | Addition | Sum of $a and $b. |
| $a - $b | Subtraction | Difference of $a and $b. |
| $a * $b | Multiplication | Product of $a and $b. |
| $a / $b | Division | Quotient of $a and $b. |
| $a % $b | Modulus | Remainder of $a divided by $b. |
The division operator ("/") returns an integer value (the result of an integer division) if the two operands are integers (or strings that get converted to integers). If either operand is a floating-point value, floating-point division is performed.
The basic assignment operator is "=". Your first inclination might be to think of this as "equal to". Don't. It really means that the the left operand gets set to the value of the expression on the rights (that is, "gets set to").
The value of an assignment expression is the value assigned. That is, the value of "$a = 3" is 3. This allows you to do some tricky things:
$a = ($b = 4) + 5; // $a is equal to 9 now, and $b has been set to 4.
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In addition to the basic assignment operator, there are "combined operators" for all of the binary arithmetic and string operators that allow you to use a value in an expression and then set its value to the result of that expression. For example:
$a = 3;
$a += 5; // sets $a to 8, as if we had said: $a = $a + 5;
$b = "Hello ";
$b .= "There!"; // sets $b to "Hello There!", just like $b = $b . "There!";
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Note that the assignment copies the original variable to the new one (assignment by value), so changes to one will not affect the other. This may also have relevance if you need to copy something like a large array inside a tight loop. PHP4 supports assignment by reference, using the $var = &$othervar; syntax, but this is not possible in PHP3. 'Assignment by reference' means that both variables end up pointing at the same data, and nothing is copied anywhere.
Bitwise operators allow you to turn specific bits within an integer on or off.
Table 10-2. Bitwise Operators
| Example | Name | Result |
|---|---|---|
| $a & $b | And | Bits that are set in both $a and $b are set. |
| $a | $b | Or | Bits that are set in either $a or $b are set. |
| $a ^ $b | Xor | Bits that are set in $a or $b but not both are set. |
| ~ $a | Not | Bits that are set in $a are not set, and vice versa. |
| $a << $b | Shift left | Shift the bits of $a $b steps to the left (each step means "multiply by two") |
| $a >> $b | Shift right | Shift the bits of $a $b steps to the right (each step means "divide by two") |
Comparison operators, as their name implies, allow you to compare two values.
Table 10-3. Comparison Operators
| Example | Name | Result |
|---|---|---|
| $a == $b | Equal | True if $a is equal to $b. |
| $a === $b | Identical | True if $a is equal to $b, and they are of the same type. (PHP4 only) |
| $a != $b | Not equal | True if $a is not equal to $b. |
| $a !== $b | Not identical | True if $a is not equal to $b, or they are not of the same type. (PHP4 only) |
| $a < $b | Less than | True if $a is strictly less than $b. |
| $a > $b | Greater than | True if $a is strictly greater than $b. |
| $a <= $b | Less than or equal to | True if $a is less than or equal to $b. |
| $a >= $b | Greater than or equal to | True if $a is greater than or equal to $b. |
Another conditional operator is the "?:" (or trinary) operator, which operates as in C and many other languages.
(expr1) ? (expr2) : (expr3);
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PHP supports one error control operator: the at sign (@). When prepended to an expression in PHP, any error messages that might be generated by that expression will be ignored.
If the track_errors feature is enabled, any error message generated by the expression will be saved in the global variable $php_errormsg. This variable will be overwritten on each error, so check early if you want to use it.
<?php
/* Intentional SQL error (extra quote): */
$res = @mysql_query ("select name, code from 'namelist") or
die ("Query failed: error was '$php_errormsg'");
?>
|
See also error_reporting().
| Warning |
|
Currently the "@" error-control operator prefix will even disable error reporting for critical errors that will terminate script execution. Among other things, this means that if you use "@" to suppress errors from a certain function and either it isn't available or has been mistyped, the script will die right there with no indication as to why. |
PHP supports one execution operator: backticks (``). Note that these are not single-quotes! PHP will attempt to execute the contents of the backticks as a shell command; the output will be returned (i.e., it won't simply be dumped to output; it can be assigned to a variable).
$output = `ls -al`;
echo "<pre>$output</pre>";
|
See also system(), passthru(), exec(), popen(), and escapeshellcmd().
PHP supports C-style pre- and post-increment and decrement operators.
Table 10-4. Increment/decrement Operators
| Example | Name | Effect |
|---|---|---|
| ++$a | Pre-increment | Increments $a by one, then returns $a. |
| $a++ | Post-increment | Returns $a, then increments $a by one. |
| --$a | Pre-decrement | Decrements $a by one, then returns $a. |
| $a-- | Post-decrement | Returns $a, then decrements $a by one. |
Here's a simple example script:
<?php
echo "<h3>Postincrement</h3>";
$a = 5;
echo "Should be 5: " . $a++ . "<br>\n";
echo "Should be 6: " . $a . "<br>\n";
echo "<h3>Preincrement</h3>";
$a = 5;
echo "Should be 6: " . ++$a . "<br>\n";
echo "Should be 6: " . $a . "<br>\n";
echo "<h3>Postdecrement</h3>";
$a = 5;
echo "Should be 5: " . $a-- . "<br>\n";
echo "Should be 4: " . $a . "<br>\n";
echo "<h3>Predecrement</h3>";
$a = 5;
echo "Should be 4: " . --$a . "<br>\n";
echo "Should be 4: " . $a . "<br>\n";
?>
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Table 10-5. Logical Operators
| Example | Name | Result |
|---|---|---|
| $a and $b | And | True if both $a and $b are true. |
| $a or $b | Or | True if either $a or $b is true. |
| $a xor $b | Or | True if either $a or $b is true, but not both. |
| ! $a | Not | True if $a is not true. |
| $a && $b | And | True if both $a and $b are true. |
| $a || $b | Or | True if either $a or $b is true. |
The reason for the two different variations of "and" and "or" operators is that they operate at different precedences. (See Operator Precedence.)
The precedence of an operator specifies how "tightly" it binds two expressions together. For example, in the expression 1 + 5 * 3, the answer is 16 and not 18 because the multiplication ("*") operator has a higher precedence than the addition ("+") operator.
The following table lists the precedence of operators with the lowest-precedence operators listed first.
Table 10-6. Operator Precedence
| Associativity | Operators |
|---|---|
| left | , |
| left | or |
| left | xor |
| left | and |
| right | |
| left | = += -= *= /= .= %= &= |= ^= ~= <<= >>= |
| left | ? : |
| left | || |
| left | && |
| left | | |
| left | ^ |
| left | & |
| non-associative | == != === !== |
| non-associative | < <= > >= |
| left | << >> |
| left | + - . |
| left | * / % |
| right | ! ~ ++ -- (int) (double) (string) (array) (object) @ |
| right | [ |
| non-associative | new |
There are two string operators. The first is the concatenation operator ('.'), which returns the concatenation of its right and left arguments. The second is the concatenating assignment operator ('.='), which appends the argument on the right side to the argument on the left side. Please read Assignment Operators for more information.
$a = "Hello ";
$b = $a . "World!"; // now $b contains "Hello World!"
$a = "Hello ";
$a .= "World!"; // now $a contains "Hello World!"
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Any PHP script is built out of a series of statements. A statement can be an assignment, a function call, a loop, a conditional statement of even a statement that does nothing (an empty statement). Statements usually end with a semicolon. In addition, statements can be grouped into a statement-group by encapsulating a group of statements with curly braces. A statement-group is a statement by itself as well. The various statement types are described in this chapter.
The if construct is one of the most important features of many languages, PHP included. It allows for conditional execution of code fragments. PHP features an if structure that is similar to that of C:
if (expr)
statement
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As described in the section about expressions, expr is evaluated to its truth value. If expr evaluates to TRUE, PHP will execute statement, and if it evaluates to FALSE - it'll ignore it.
The following example would display a is bigger than b if $a is bigger than $b:
if ($a > $b)
print "a is bigger than b";
|
Often you'd want to have more than one statement to be executed conditionally. Of course, there's no need to wrap each statement with an if clause. Instead, you can group several statements into a statement group. For example, this code would display a is bigger than b if $a is bigger than $b, and would then assign the value of $a into $b:
if ($a > $b) {
print "a is bigger than b";
$b = $a;
}
|
If statements can be nested indefinitely within other if statements, which provides you with complete flexibility for conditional execution of the various parts of your program.
Often you'd want to execute a statement if a certain condition is met, and a different statement if the condition is not met. This is what else is for. else extends an if statement to execute a statement in case the expression in the if statement evaluates to FALSE. For example, the following code would display a is bigger than b if $a is bigger than $b, and a is NOT bigger than b otherwise:
if ($a > $b) {
print "a is bigger than b";
} else {
print "a is NOT bigger than b";
}
|
elseif, as its name suggests, is a combination of if and else. Like else, it extends an if statement to execute a different statement in case the original if expression evaluates to FALSE. However, unlike else, it will execute that alternative expression only if the elseif conditional expression evaluates to TRUE. For example, the following code would display a is bigger than b, a equal to b or a is smaller than b:
if ($a > $b) {
print "a is bigger than b";
} elseif ($a == $b) {
print "a is equal to b";
} else {
print "a is smaller than b";
}
|
There may be several elseifs within the same if statement. The first elseif expression (if any) that evaluates to true would be executed. In PHP, you can also write 'else if' (in two words) and the behavior would be identical to the one of 'elseif' (in a single word). The syntactic meaning is slightly different (if you're familiar with C, this is the same behavior) but the bottom line is that both would result in exactly the same behavior.
The elseif statement is only executed if the preceding if expression and any preceding elseif expressions evaluated to FALSE, and the current elseif expression evaluated to TRUE.
PHP offers an alternative syntax for some of its control structures; namely, if, while, for, and switch. In each case, the basic form of the alternate syntax is to change the opening brace to a colon (:) and the closing brace to endif;, endwhile;, endfor;, or endswitch;, respectively.
<?php if ($a == 5): ?>
A is equal to 5
<?php endif; ?>
|
In the above example, the HTML block "A = 5" is nested within an if statement written in the alternative syntax. The HTML block would be displayed only if $a is equal to 5.
The alternative syntax applies to else and elseif as well. The following is an if structure with elseif and else in the alternative format:
if ($a == 5):
print "a equals 5";
print "...";
elseif ($a == 6):
print "a equals 6";
print "!!!";
else:
print "a is neither 5 nor 6";
endif;
|
while loops are the simplest type of loop in PHP. They behave just like their C counterparts. The basic form of a while statement is:
while (expr) statement
|
The meaning of a while statement is simple. It tells PHP to execute the nested statement(s) repeatedly, as long as the while expression evaluates to TRUE. The value of the expression is checked each time at the beginning of the loop, so even if this value changes during the execution of the nested statement(s), execution will not stop until the end of the iteration (each time PHP runs the statements in the loop is one iteration). Sometimes, if the while expression evaluates to FALSE from the very beginning, the nested statement(s) won't even be run once.
Like with the if statement, you can group multiple statements within the same while loop by surrounding a group of statements with curly braces, or by using the alternate syntax:
while (expr): statement ... endwhile;
|
The following examples are identical, and both print numbers from 1 to 10:
/* example 1 */
$i = 1;
while ($i <= 10) {
print $i++; /* the printed value would be
$i before the increment
(post-increment) */
}
/* example 2 */
$i = 1;
while ($i <= 10):
print $i;
$i++;
endwhile;
|
do..while loops are very similar to while loops, except the truth expression is checked at the end of each iteration instead of in the beginning. The main difference from regular while loops is that the first iteration of a do..while loop is guarenteed to run (the truth expression is only checked at the end of the iteration), whereas it's may not necessarily run with a regular while loop (the truth expression is checked at the beginning of each iteration, if it evaluates to FALSE right from the beginning, the loop execution would end immediately).
There is just one syntax for do..while loops:
$i = 0;
do {
print $i;
} while ($i>0);
|
The above loop would run one time exactly, since after the first iteration, when truth expression is checked, it evaluates to FALSE ($i is not bigger than 0) and the loop execution ends.
Advanced C users may be familiar with a different usage of the do..while loop, to allow stopping execution in the middle of code blocks, by encapsulating them with do..while(0), and using the break statement. The following code fragment demonstrates this:
do {
if ($i < 5) {
print "i is not big enough";
break;
}
$i *= $factor;
if ($i < $minimum_limit) {
break;
}
print "i is ok";
...process i...
} while(0);
|
Don't worry if you don't understand this right away or at all. You can code scripts and even powerful scripts without using this `feature'.
for loops are the most complex loops in PHP. They behave like their C counterparts. The syntax of a for loop is:
for (expr1; expr2; expr3) statement
|
The first expression (expr1) is evaluated (executed) once unconditionally at the beginning of the loop.
In the beginning of each iteration, expr2 is evaluated. If it evaluates to TRUE, the loop continues and the nested statement(s) are executed. If it evaluates to FALSE, the execution of the loop ends.
At the end of each iteration, expr3 is evaluated (executed).
Each of the expressions can be empty. expr2 being empty means the loop should be run indefinitely (PHP implicitly considers it as TRUE, like C). This may not be as useless as you might think, since often you'd want to end the loop using a conditional break statement instead of using the for truth expression.
Consider the following examples. All of them display numbers from 1 to 10:
/* example 1 */
for ($i = 1; $i <= 10; $i++) {
print $i;
}
/* example 2 */
for ($i = 1;;$i++) {
if ($i > 10) {
break;
}
print $i;
}
/* example 3 */
$i = 1;
for (;;) {
if ($i > 10) {
break;
}
print $i;
$i++;
}
/* example 4 */
for ($i = 1; $i <= 10; print $i, $i++) ;
|
Of course, the first example appears to be the nicest one (or perhaps the fourth), but you may find that being able to use empty expressions in for loops comes in handy in many occasions.
PHP also supports the alternate "colon syntax" for for loops.
for (expr1; expr2; expr3): statement; ...; endfor;
|
Other languages have a foreach statement to traverse an array or hash. PHP3 has no such construct; PHP4 does (see foreach). In PHP3, you can combine while with the list() and each() functions to achieve the same effect. See the documentation for these functions for an example.
PHP4 (not PHP3) includes a foreach construct, much like perl and some other languages. This simply gives an easy way to iterate over arrays. There are two syntaxes; the second is a minor but useful extension of the first:
foreach(array_expression as $value) statement
foreach(array_expression as $key => $value) statement
|
The first form loops over the array given by array_expression. On each loop, the value of the current element is assigned to $value and the internal array pointer is advanced by one (so on the next loop, you'll be looking at the next element).
The second form does the same thing, except that the current element's key will be assigned to the variable $key on each loop.
Note: When foreach first starts executing, the internal array pointer is automatically reset to the first element of the array. This means that you do not need to call reset() before a foreach loop.
Note: Also note that foreach operates on a copy of the specified array, not the array itself, therefore the array pointer is not modified like with the each construct.
You may have noticed that the following are functionally identical:
reset ($arr);
while (list(, $value) = each ($arr)) {
echo "Value: $value<br>\n";
}
foreach ($arr as $value) {
echo "Value: $value<br>\n";
}
|
reset ($arr);
while (list($key, $value) = each ($arr)) {
echo "Key: $key; Value: $value<br>\n";
}
foreach ($arr as $key => $value) {
echo "Key: $key; Value: $value<br>\n";
}
|
Some more examples to demonstrate usages:
/* foreach example 1: value only */
$a = array (1, 2, 3, 17);
foreach ($a as $v) {
print "Current value of \$a: $v.\n";
}
/* foreach example 2: value (with key printed for illustration) */
$a = array (1, 2, 3, 17);
$i = 0; /* for illustrative purposes only */
foreach($a as $v) {
print "\$a[$i] => $k.\n";
}
/* foreach example 3: key and value */
$a = array (
"one" => 1,
"two" => 2,
"three" => 3,
"seventeen" => 17
);
foreach($a as $k => $v) {
print "\$a[$k] => $v.\n";
}
|
break ends execution of the current for, while, or switch structure.
break accepts an optional numeric argument which tells it how many nested enclosing structures are to be broken out of.
$arr = array ('one', 'two', 'three', 'four', 'stop', 'five');
while (list (, $val) = each ($arr)) {
if ($val == 'stop') {
break; /* You could also write 'break 1;' here. */
}
echo "$val<br>\n";
}
/* Using the optional argument. */
$i = 0;
while (++$i) {
switch ($i) {
case 5:
echo "At 5<br>\n";
break 1; /* Exit only the switch. */
case 10:
echo "At 10; quitting<br>\n";
break 2; /* Exit the switch and the while. */
default:
break;
}
}
|
continue is used within looping structures to skip the rest of the current loop iteration and continue execution at the beginning of the next iteration.
continue accepts an optional numeric argument which tells it how many levels of enclosing loops it should skip to the end of.
while (list ($key, $value) = each ($arr)) {
if (!($key % 2)) { // skip odd members
continue;
}
do_something_odd ($value);
}
$i = 0;
while ($i++ < 5) {
echo "Outer<br>\n";
while (1) {
echo " Middle<br>\n";
while (1) {
echo " Inner<br>\n";
continue 3;
}
echo "This never gets output.<br>\n";
}
echo "Neither does this.<br>\n";
}
|
The switch statement is similar to a series of IF statements on the same expression. In many occasions, you may want to compare the same variable (or expression) with many different values, and execute a different piece of code depending on which value it equals to. This is exactly what the switch statement is for.
The following two examples are two different ways to write the same thing, one using a series of if statements, and the other using the switch statement:
if ($i == 0) {
print "i equals 0";
}
if ($i == 1) {
print "i equals 1";
}
if ($i == 2) {
print "i equals 2";
}
switch ($i) {
case 0:
print "i equals 0";
break;
case 1:
print "i equals 1";
break;
case 2:
print "i equals 2";
break;
}
|
It is important to understand how the switch statement is executed in order to avoid mistakes. The switch statement executes line by line (actually, statement by statement). In the beginning, no code is executed. Only when a case statement is found with a value that matches the value of the switch expression does PHP begin to execute the statements. PHP continues to execute the statements until the end of the switch block, or the first time it sees a break statement. If you don't write a break statement at the end of a case's statement list, PHP will go on executing the statements of the following case. For example:
switch ($i) {
case 0:
print "i equals 0";
case 1:
print "i equals 1";
case 2:
print "i equals 2";
}
|
Here, if $i equals to 0, PHP would execute all of the print statements! If $i equals to 1, PHP would execute the last two print statements, and only if $i equals to 2, you'd get the 'expected' behavior and only 'i equals 2' would be displayed. So, it's important not to forget break statements (even though you may want to avoid supplying them on purpose under certain circumstances).
In a switch statement, the condition is evaluated only once and the result is compared to each case statement. In an elseif statement, the condition is evaluated again. If your condition is more complicated than a simple compare and/or is in a tight loop, a switch may be faster.
The statement list for a case can also be empty, which simply passes control into the statement list for the next case.
switch ($i) {
case 0:
case 1:
case 2:
print "i is less than 3 but not negative";
break;
case 3:
print "i is 3";
}
|
A special case is the default case. This case matches anything that wasn't matched by the other cases. For example:
switch ($i) {
case 0:
print "i equals 0";
break;
case 1:
print "i equals 1";
break;
case 2:
print "i equals 2";
break;
default:
print "i is not equal to 0, 1 or 2";
}
|
The case expression may be any expression that evaluates to a simple type, that is, integer or floating-point numbers and strings. Arrays or objects cannot be used here unless they are dereferenced to a simple type.
The alternative syntax for control structures is supported with switches. For more information, see Alternative syntax for control structures .
switch ($i):
case 0:
print "i equals 0";
break;
case 1:
print "i equals 1";
break;
case 2:
print "i equals 2";
break;
default:
print "i is not equal to 0, 1 or 2";
endswitch;
|
The require() statement replaces itself with the specified file, much like the C preprocessor's #include works.
If "URL fopen wrappers" are enabled in PHP (which they are in the default configuration), you can specify the file to be require()ed using an URL instead of a local pathname. See Remote files and fopen() for more information.
An important note about how this works is that when a file is include()ed or require()ed, parsing drops out of PHP mode and into HTML mode at the beginning of the target file, and resumes PHP mode again at the end. For this reason, any code inside the target file which should be executed as PHP code must be enclosed within valid PHP start and end tags.
require() is not actually a function in PHP; rather, it is a language construct. It is subject to some different rules than functions are. For instance, require() is not subject to any containing control structures. For another, it does not return any value; attempting to read a return value from a require() call results in a parse error.
Unlike include(), require() will always read in the target file, even if the line it's on never executes. If you want to conditionally include a file, use include(). The conditional statement won't affect the require(). However, if the line on which the require() occurs is not executed, neither will any of the code in the target file be executed.
Similarly, looping structures do not affect the behaviour of require(). Although the code contained in the target file is still subject to the loop, the require() itself happens only once.
This means that you can't put a require() statement inside of a loop structure and expect it to include the contents of a different file on each iteration. To do that, use an include() statement.
require ('header.inc');
|
When a file is require()ed, the code it contains inherits the variable scope of the line on which the require() occurs. Any variables available at that line in the calling file will be available within the called file. If the require() occurs inside a function within the calling file, then all of the code contained in the called file will behave as though it had been defined inside that function.
If the require()ed file is called via HTTP using the fopen wrappers, and if the target server interprets the target file as PHP code, variables may be passed to the require()ed file using an URL request string as used with HTTP GET. This is not strictly speaking the same thing as require()ing the file and having it inherit the parent file's variable scope; the script is actually being run on the remote server and the result is then being included into the local script.
/* This example assumes that someserver is configured to parse .php
* files and not .txt files. Also, 'works' here means that the variables
* $varone and $vartwo are available within the require()ed file. */
/* Won't work; file.txt wasn't handled by someserver. */
require ("http://someserver/file.txt?varone=1&vartwo=2");
/* Won't work; looks for a file named 'file.php?varone=1&vartwo=2'
* on the local filesystem. */
require ("file.php?varone=1&vartwo=2");
/* Works. */
require ("http://someserver/file.php?varone=1&vartwo=2");
$varone = 1;
$vartwo = 2;
require ("file.txt"); /* Works. */
require ("file.php"); /* Works. */
|
In PHP3, it is possible to execute a return statement inside a require()ed file, as long as that statement occurs in the global scope of the require()ed file. It may not occur within any block (meaning inside braces ({}). In PHP4, however, this ability has been discontinued. If you need this functionality, see include().
See also include(), require_once(), include_once(), readfile(), and virtual().
The include() statement includes and evaluates the specified file.
If "URL fopen wrappers" are enabled in PHP (which they are in the default configuration), you can specify the file to be include()ed using an URL instead of a local pathname. See Remote files and fopen() for more information.
An important note about how this works is that when a file is include()ed or require()ed, parsing drops out of PHP mode and into HTML mode at the beginning of the target file, and resumes again at the end. For this reason, any code inside the target file which should be executed as PHP code must be enclosed within valid PHP start and end tags.
This happens each time the include() statement is encountered, so you can use an include() statement within a looping structure to include a number of different files.
$files = array ('first.inc', 'second.inc', 'third.inc');
for ($i = 0; $i < count($files); $i++) {
include $files[$i];
}
|
include() differs from require() in that the include statement is re-evaluated each time it is encountered (and only when it is being executed), whereas the require() statement is replaced by the required file when it is first encountered, whether the contents of the file will be evaluated or not (for example, if it is inside an if statement whose condition evaluated to false).
Because include() is a special language construct, you must enclose it within a statement block if it is inside a conditional block.
/* This is WRONG and will not work as desired. */
if ($condition)
include($file);
else
include($other);
/* This is CORRECT. */
if ($condition) {
include($file);
} else {
include($other);
}
|
In both PHP3 and PHP4, it is possible to execute a return statement inside an include()ed file, in order to terminate processing in that file and return to the script which called it. Some differences in the way this works exist, however. The first is that in PHP3, the return may not appear inside a block unless it's a function block, in which case the return applies to that function and not the whole file. In PHP4, however, this restriction does not exist. Also, PHP4 allows you to return values from include()ed files. You can take the value of the include() call as you would a normal function. This generates a parse error in PHP3.
|
Example 11-1. include() in PHP3 and PHP4 Assume the existence of the following file (named test.inc) in the same directory as the main file:
Assume that the main file (main.html) contains the following:
When main.html is called in PHP3, it will generate a parse error on line 2; you can't take the value of an include() in PHP3. In PHP4, however, the result will be:
Now, assume that main.html has been altered to contain the following:
In PHP4, the output will be:
The above parse error is a result of the fact that the return statement is enclosed in a non-function block within test.inc. When the return is moved outside of the block, the output is:
The spurious '27' is due to the fact that PHP3 does not support returning values from files like that. |
When a file is include()ed, the code it contains inherits the variable scope of the line on which the include() occurs. Any variables available at that line in the calling file will be available within the called file. If the include() occurs inside a function within the calling file, then all of the code contained in the called file will behave as though it had been defined inside that function.
If the include()ed file is called via HTTP using the fopen wrappers, and if the target server interprets the target file as PHP code, variables may be passed to the include()ed file using an URL request string as used with HTTP GET. This is not strictly speaking the same thing as include()ing the file and having it inherit the parent file's variable scope; the script is actually being run on the remote server and the result is then being included into the local script.
/* This example assumes that someserver is configured to parse .php
* files and not .txt files. Also, 'works' here means that the variables
* $varone and $vartwo are available within the include()ed file. */
/* Won't work; file.txt wasn't handled by someserver. */
include ("http://someserver/file.txt?varone=1&vartwo=2");
/* Won't work; looks for a file named 'file.php?varone=1&vartwo=2'
* on the local filesystem. */
include ("file.php?varone=1&vartwo=2");
/* Works. */
include ("http://someserver/file.php?varone=1&vartwo=2");
$varone = 1;
$vartwo = 2;
include ("file.txt"); /* Works. */
include ("file.php"); /* Works. */
|
See also require(), require_once(), include_once(), readfile(), and virtual().
The require_once() statement replaces itself with the specified file, much like the C preprocessor's #include works, and in that respect is similar to the require() statement. The main difference is that in an inclusion chain, the use of require_once() will assure that the code is added to your script only once, and avoid clashes with variable values or function names that can happen.
For example, if you create the following 2 include files utils.inc and foolib.inc
|
Example 11-2. utils.inc
|
|
Example 11-3. foolib.inc
|
|
Example 11-4. cause_error_require.php
|
GLOBALS ARE NICE GLOBALS ARE NICE Fatal error: Cannot redeclare causeerror() in utils.inc on line 5 |
|
Example 11-5. foolib.inc (fixed)
|
|
Example 11-6. avoid_error_require_once.php
|
GLOBALS ARE NICE
this is requiring globals.inc again which is also
required in foolib.inc
Running goodTea: Oolong tea tastes good!
Printing foo:
Array
(
[0] => 1
[1] => Array
(
[0] => complex
[1] => quaternion
)
)
|
Also note that, analogous to the behavior of the #include of the C preprocessor, this statement acts at "compile time", e.g. when the script is parsed and before it is executed, and should not be used for parts of the script that need to be inserted dynamically during its execution. You should use include_once() or include() for that purpose.
For more examples on using require_once() and include_once(), look at the PEAR code included in the latest PHP source code distributions.
See also: require(), include(), include_once(), get_required_files(), get_included_files(), readfile(), and virtual().
The include_once() statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include() statement, with the important difference that if the code from a file has already been included, it will not be included again.
As mentioned in the require_once() description, the include_once() should be used in the cases in which the same file might be included and evaluated more than once during a particular execution of a script, and you want to be sure that it is included exactly once to avoid problems with function redefinitions, variable value reassignments, etc.
For more examples on using require_once() and include_once(), look at the PEAR code included in the latest PHP source code distributions.
See also: require(), include(), require_once(), get_required_files(), get_included_files(), readfile(), and virtual().
A function may be defined using syntax such as the following:
function foo ($arg_1, $arg_2, ..., $arg_n) {
echo "Example function.\n";
return $retval;
}
|
Any valid PHP code may appear inside a function, even other functions and class definitions.
In PHP3, functions must be defined before they are referenced. No such requirement exists in PHP4.
PHP does not support function overloading, nor is it possible to undefine or redefine previously-declared functions.
PHP3 does not support variable numbers of arguments to functions, although default arguments are supported (see Default argument values for more information). PHP4 supports both: see Variable-length argument lists and the function references for func_num_args(), func_get_arg(), and func_get_args() for more information.
Information may be passed to functions via the argument list, which is a comma-delimited list of variables and/or constants.
PHP supports passing arguments by value (the default), passing by reference, and default argument values. Variable-length argument lists are supported only in PHP4 and later; see Variable-length argument lists and the function references for func_num_args(), func_get_arg(), and func_get_args() for more information. A similar effect can be achieved in PHP3 by passing an array of arguments to a function:
function takes_array($input) {
echo "$input[0] + $input[1] = ", $input[0]+$input[1];
}
|
By default, function arguments are passed by value (so that if you change the value of the argument within the function, it does not get changed outside of the function). If you wish to allow a function to modify its arguments, you must pass them by reference.
If you want an argument to a function to always be passed by reference, you can prepend an ampersand (&) to the argument name in the function definition:
function add_some_extra(&$string) {
$string .= 'and something extra.';
}
$str = 'This is a string, ';
add_some_extra($str);
echo $str; // outputs 'This is a string, and something extra.'
|
If you wish to pass a variable by reference to a function which does not do this by default, you may prepend an ampersand to the argument name in the function call:
function foo ($bar) {
$bar .= ' and something extra.';
}
$str = 'This is a string, ';
foo ($str);
echo $str; // outputs 'This is a string, '
foo (&$str);
echo $str; // outputs 'This is a string, and something extra.'
|
A function may define C++-style default values for scalar arguments as follows:
function makecoffee ($type = "cappucino") {
return "Making a cup of $type.\n";
}
echo makecoffee ();
echo makecoffee ("espresso");
|
The output from the above snippet is:
Making a cup of cappucino.
Making a cup of espresso.
|
The default value must be a constant expression, not (for example) a variable or class member.
Note that when using default arguments, any defaults should be on the right side of any non-default arguments; otherwise, things will not work as expected. Consider the following code snippet:
function makeyogurt ($type = "acidophilus", $flavour) {
return "Making a bowl of $type $flavour.\n";
}
echo makeyogurt ("raspberry"); // won't work as expected
|
The output of the above example is:
Warning: Missing argument 2 in call to makeyogurt() in
/usr/local/etc/httpd/htdocs/php3test/functest.html on line 41
Making a bowl of raspberry .
|
Now, compare the above with this:
function makeyogurt ($flavour, $type = "acidophilus") {
return "Making a bowl of $type $flavour.\n";
}
echo makeyogurt ("raspberry"); // works as expected
|
The output of this example is:
Making a bowl of acidophilus raspberry.
|
PHP4 has support for variable-length argument lists in user-defined functions. This is really quite easy, using the func_num_args(), func_get_arg(), and func_get_args() functions.
No special syntax is required, and argument lists may still be explicitly provided with function definitions and will behave as normal.
Values are returned by using the optional return statement. Any type may be returned, including lists and objects.
function square ($num) {
return $num * $num;
}
echo square (4); // outputs '16'.
|
You can't return multiple values from a function, but similar results can be obtained by returning a list.
function small_numbers() {
return array (0, 1, 2);
}
list ($zero, $one, $two) = small_numbers();
|
To return a reference from a function, you have to use the reference operator & in both the function declaration and when assigning the return value to a variable:
function &returns_reference() {
return &$someref;
}
$newref = &returns_reference();
|
The old_function statement allows you to declare a function using a syntax identical to PHP/FI2 (except you must replace 'function' with 'old_function'.
This is a deprecated feature, and should only be used by the PHP/FI2->PHP3 convertor.
| Warning |
|
Functions declared as old_function cannot be called from PHP's internal code. Among other things, this means you can't use them in functions such as usort(), array_walk(), and register_shutdown_function(). You can get around this limitation by writing a wrapper function (in normal PHP3 form) to call the old_function. |
PHP supports the concept of variable functions. This means that if a variable name has parentheses appended to it, PHP will look for a function with the same name as whatever the variable evaluates to, and will attempt to execute it. Among other things, this can be used to implement callbacks, function tables, and so forth.
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Example 12-1. Variable function example
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A class is a collection of variables and functions working with these variables. A class is defined using the following syntax:
<?php
class Cart {
var $items; // Items in our shopping cart
// Add $num articles of $artnr to the cart
function add_item ($artnr, $num) {
$this->items[$artnr] += $num;
}
// Take $num articles of $artnr out of the cart
function remove_item ($artnr, $num) {
if ($this->items[$artnr] > $num) {
$this->items[$artnr] -= $num;
return true;
} else {
return false;
}
}
}
?>
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This defines a class named Cart that consists of an associative array of articles in the cart and two functions to add and remove items from this cart.
Classes are types, that is, they are blueprints for actual variables. You have to create a variable of the desired type with the new operator.
$cart = new Cart;
$cart->add_item("10", 1);
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This creates an object $cart of the class Cart. The function add_item() of that object is being called to add 1 item of article number 10 to the cart.
Classes can be extensions of other classes. The extended or derived class has all variables and functions of the base class and what you add in the extended definition. This is done using the extends keyword. Multiple inheritance is not supported.
class Named_Cart extends Cart {
var $owner;
function set_owner ($name) {
$this->owner = $name;
}
}
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This defines a class Named_Cart that has all variables and functions of Cart plus an additional variable $owner and an additional function set_owner(). You create a named cart the usual way and can now set and get the carts owner. You can still use normal cart functions on named carts:
$ncart = new Named_Cart; // Create a named cart
$ncart->set_owner ("kris"); // Name that cart
print $ncart->owner; // print the cart owners name
$ncart->add_item ("10", 1); // (inherited functionality from cart)
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Within functions of a class the variable $this means this object. You have to use $this->something to access any variable or function named something within your current object.
Constructors are functions in a class that are automatically called when you create a new instance of a class. A function becomes a constructor when it has the same name as the class.
class Auto_Cart extends Cart {
function Auto_Cart () {
$this->add_item ("10", 1);
}
}
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This defines a class Auto_Cart that is a Cart plus a constructor which initializes the cart with one item of article number "10" each time a new Auto_Cart is being made with "new". Constructors can also take arguments and these arguments can be optional, which makes them much more useful.
class Constructor_Cart extends Cart {
function Constructor_Cart ($item = "10", $num = 1) {
$this->add_item ($item, $num);
}
}
// Shop the same old boring stuff.
$default_cart = new Constructor_Cart;
// Shop for real...
$different_cart = new Constructor_Cart ("20", 17);
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| Caution |
|
For derived classes, the constructor of the parent class is not automatically called when the derived class's constructor is called. |
References in PHP are means to call same variable content with different names. They are not like C pointers, they are symbol table aliases. Note that in PHP, variable names and variable content are different, so same content can have different names. The most close analogy is Unix filenames and files - variable names are directory entries, while variable contents is the file itself. References can be thought of as hardlinking in Unix filesystem.
PHP references allow you to make two variables to refer to the same content. Meaning, when you do:
$a =& $b
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Note: $a and $b are completely equal here, that's not $a is pointing to $b or vice versa, that's $a and $b pointing to the same place.
The second thing references do is to pass variables by-reference. This is done by making local function variable and caller variable to be reference to the same content. Example:
function foo (&$var) {
$var++;
}
$a=5;
foo ($a);
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The third thing reference can do is return by-reference.
As said above, references aren't pointers. That means, the following construct won't do what you expect:
function foo (&$var) {
$var =& $GLOBALS["baz"];
}
foo($bar);
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What will happen that $var in foo will be bound with $bar in caller, but then it will be re-bound with $GLOBALS["baz"]. There's no way to bind $bar in the caller to something else using reference mechanism, since $bar is not available in the function foo (it is represented by $var, but $var has only variable contents and not name-to-value binding in the calling symbol table).
Returning by-refernce it is useful when you want to use function to find variable which should be bound to. When returning references, use this syntax:
function &find_var ($param) {
...code...
return $found_var;
}
$foo =& find_var ($bar);
$foo->x = 2;
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Note: Unlike parameter passing, here you have to use & in both places - to indicate that you return by-reference, not a copy as usual, and to indicate than reference binding and not usual assignment should be done for $foo.
When you unset the reference, you just break the binding between variable name and variable content. This does not mean that variable content will be destroyed. For example:
$a = 1;
$b =& $a;
unset ($a);
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Again, it might be useful to think about this as analogous to Unix unlink call.
Many syntax constructs in PHP are implemented via referencing mechanisms, so everything told above about reference binding also apply to these constructs. Some constructs, like passing and returning by-reference, are mentioned above. Other constructs that use references are:
When you declare variable as global $var you are in fact creating reference to a global variable. That means, this is the same as:
$var =& $GLOBALS["var"];
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That means, for example, that unsetting $var won't unset global variable.
There are several types of errors and warnings in PHP. They are:
Table 15-1. PHP error types
| Value | Constant | Description | Note |
|---|---|---|---|
| 1 | E_ERROR | fatal run-time errors | |
| 2 | E_WARNING | run-time warnings (non fatal errors) | |
| 4 | E_PARSE | compile-time parse errors | |
| 8 | E_NOTICE | run-time notices (less serious than warnings) | |
| 16 | E_CORE_ERROR | fatal errors that occur during PHP's initial startup | PHP 4 only |
| 32 | E_CORE_WARNING | warnings (non fatal errors) that occur during PHP's initial startup | PHP 4 only |
| 64 | E_COMPILE_ERROR | fatal compile-time errors | PHP 4 only |
| 128 | E_COMPILE_WARNING | compile-time warnings (non fatal errors) | PHP 4 only |
| 256 | E_USER_ERROR | user-generated error message | PHP 4 only |
| 512 | E_USER_WARNING | user-generated warning message | PHP 4 only |
| 1024 | E_USER_NOTICE | user-generated notice message | PHP 4 only |
| E_ALL | all of the above, as supported |
The above values (either numerical or symbolic) are used to build up a bitmask that specifies which errors to report. You can use the bitwise operators to combine these values or mask out certain types of errors. Note that only '|', '~', '!', and '&' will be understood within php.ini, however, and that no bitwise operators will be understood within php3.ini.
In PHP 4, the default error_reporting setting is E_ALL & ~E_NOTICE, meaning to display all errors and warnings which are not E_NOTICE-level. In PHP 3, the default setting is (E_ERROR | E_WARNING | E_PARSE), meaning the same thing. Note, however, that since constants are not supported in PHP 3's php3.ini, the error_reporting setting there must be numeric; hence, it is 7.
The initial setting can be changed in the ini file with the error_reporting directive, in your Apache httpd.conf file with the php_error_reporting (php3_error_reporting for PHP 3) directive, and lastly it may be set at runtime within a script by using the error_reporting() function.
| Warning |
|
When upgrading code or servers from PHP 3 to PHP 4 you should check these settings and calls to error_reporting() or you might disable reporting the new error types, especially E_COMPILE_ERROR. This may lead to empty documents without any feedback of what happened or where to look for the problem. |
All PHP expressions can also be called with the "@" prefix, which turns off error reporting for that particular expression. If an error occurred during such an expression and the track_errors feature is enabled, you can find the error message in the global variable $php_errormsg.
| Warning |
|
Currently the @ error-control operator prefix will even disable error reporting for critical errors that will terminate script execution. Among other things, this means that if you use @ to suppress errors from a certain function and either it isn't available or has been mistyped, the script will die right there with no indication as to why. |
PHP is not limited to creating just HTML output. It can also be used to create and manipulate image files in a variety of different image formats, including gif, png, jpg, wbmp, and xpm. Even more convenient, php can output image streams directly to a browser. You will need to compile PHP with the GD library of image functions for this to work. GD and PHP may also require other libraries, depending on which image formats you want to work with.
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Example 16-1. GIF creation with PHP
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The HTTP Authentication hooks in PHP are only available when it is running as an Apache module and is hence not available in the CGI version. In an Apache module PHP script, it is possible to use the Header() function to send an "Authentication Required" message to the client browser causing it to pop up a Username/Password input window. Once the user has filled in a username and a password, the URL containing the PHP script will be called again with the variables, $PHP_AUTH_USER, $PHP_AUTH_PW and $PHP_AUTH_TYPE set to the user name, password and authentication type respectively. Only "Basic" authentication is supported at this point. See the Header() function for more information.
An example script fragment which would force client authentication on a page would be the following:
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Example 17-1. HTTP Authentication example
|
Instead of simply printing out the $PHP_AUTH_USER and $PHP_AUTH_PW, you would probably want to check the username and password for validity. Perhaps by sending a query to a database, or by looking up the user in a dbm file.
Watch out for buggy Internet Explorer browsers out there. They seem very picky about the order of the headers. Sending the WWW-Authenticate header before the HTTP/1.0 401 header seems to do the trick for now.
In order to prevent someone from writing a script which reveals the password for a page that was authenticated through a traditional external mechanism, the PHP_AUTH variables will not be set if external authentication is enabled for that particular page. In this case, the $REMOTE_USER variable can be used to identify the externally-authenticated user.
Note, however, that the above does not prevent someone who controls a non-authenticated URL from stealing passwords from authenticated URLs on the same server.
Both Netscape and Internet Explorer will clear the local browser window's authentication cache for the realm upon receiving a server response of 401. This can effectively "log out" a user, forcing them to re-enter their username and password. Some people use this to "time out" logins, or provide a "log-out" button.
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Example 17-2. HTTP Authentication example forcing a new name/password
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This behavior is not required by the HTTP Basic authentication standard, so you should never depend on this. Testing with Lynx has shown that Lynx does not clear the authentication credentials with a 401 server response, so pressing back and then forward again will open the resource (as long as the credential requirements haven't changed).
Also note that this does not work using Microsoft's IIS server and the CGI version of PHP due to a limitation of IIS.
PHP transparently supports HTTP cookies. Cookies are a mechanism for storing data in the remote browser and thus tracking or identifying return users. You can set cookies using the setcookie() function. Cookies are part of the HTTP header, so setcookie() must be called before any output is sent to the browser. This is the same limitation that header() has.
Any cookies sent to you from the client will automatically be turned into a PHP variable just like GET and POST method data. If you wish to assign multiple values to a single cookie, just add [] to the cookie name. For more details see the setcookie() function.
PHP is capable of receiving file uploads from any RFC-1867 compliant browser (which includes Netscape Navigator 3 or later, Microsoft Internet Explorer 3 with a patch from Microsoft, or later without a patch). This feature lets people upload both text and binary files. With PHP's authentication and file manipulation functions, you have full control over who is allowed to upload and what is to be done with the file once it has been uploaded.
Note that PHP also supports PUT-method file uploads as used by Netscape Composer and W3C's Amaya clients. See the PUT Method Support for more details.
A file upload screen can be built by creating a special form which looks something like this:
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Example 19-1. File Upload Form
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$userfile - The temporary filename in which the uploaded file was stored on the server machine.
$userfile_name - The original name or path of the file on the sender's system.
$userfile_size - The size of the uploaded file in bytes.
$userfile_type - The mime type of the file if the browser provided this information. An example would be "image/gif".
Files will by default be stored in the server's default temporary directory. This can be changed by setting the environment variable TMPDIR in the environment in which PHP runs. Setting it using putenv() from within a PHP script will not work.
The PHP script which receives the uploaded file should implement whatever logic is necessary for determining what should be done with the uploaded file. You can for example use the $file_size variable to throw away any files that are either too small or too big. You could use the $file_type variable to throw away any files that didn't match a certain type criteria. Whatever the logic, you should either delete the file from the temporary directory or move it elsewhere.
The file will be deleted from the temporary directory at the end of the request if it has not been moved away or renamed.
The MAX_FILE_SIZE item cannot specify a file size greater than the file size that has been set in the upload_max_filesize in the PHP3.ini file or the corresponding php3_upload_max_filesize Apache .conf directive. The default is 2 Megabytes.
Please note that the CERN httpd seems to strip off everything starting at the first whitespace in the content-type mime header it gets from the client. As long as this is the case, CERN httpd will not support the file upload feature.
It is possible to upload multiple files simultaneously and have the information organized automatically in arrays for you. To do so, you need to use the same array submission syntax in the HTML form as you do with multiple selects and checkboxes:
Note: Support for multiple file uploads was added in version 3.0.10.
|
Example 19-2. Uploading multiple files
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When the above form is submitted, the arrays $userfile, $userfile_name, and $userfile_size will be formed in the global scope (as well as in $HTTP_POST_FILES ($HTTP_POST_VARS in PHP 3)). Each of these will be a numerically indexed array of the appropriate values for the submitted files.
For instance, assume that the filenames /home/test/review.html and /home/test/xwp.out are submitted. In this case, $userfile_name[0] would contain the value review.html, and $userfile_name[1] would contain the value xwp.out. Similarly, $userfile_size[0] would contain review.html's filesize, and so forth.
$userfile['name'][0], $userfile['tmp_name'][0], $userfile['size'][0], and $userfile['type'][0] are also set.
PHP provides support for the HTTP PUT method used by clients such as Netscape Composer and W3C Amaya. PUT requests are much simpler than a file upload and they look something like this:
PUT /path/filename.html HTTP/1.1
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This would normally mean that the remote client would like to save the content that follows as: /path/filename.html in your web tree. It is obviously not a good idea for Apache or PHP to automatically let everybody overwrite any files in your web tree. So, to handle such a request you have to first tell your web server that you want a certain PHP script to handle the request. In Apache you do this with the Script directive. It can be placed almost anywhere in your Apache configuration file. A common place is inside a <Directory> block or perhaps inside a <Virtualhost> block. A line like this would do the trick:
Script PUT /put.php3
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This tells Apache to send all PUT requests for URIs that match the context in which you put this line to the put.php3 script. This assumes, of course, that you have PHP enabled for the .php3 extension and PHP is active.
Inside your put.php3 file you would then do something like this:
<? copy($PHP_UPLOADED_FILE_NAME,$DOCUMENT_ROOT.$REQUEST_URI); ?>
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This would copy the file to the location requested by the remote client. You would probably want to perform some checks and/or authenticate the user before performing this file copy. The only trick here is that when PHP sees a PUT-method request it stores the uploaded file in a temporary file just like those handled but the POST-method. When the request ends, this temporary file is deleted. So, your PUT handling PHP script has to copy that file somewhere. The filename of this temporary file is in the $PHP_PUT_FILENAME variable, and you can see the suggested destination filename in the $REQUEST_URI (may vary on non-Apache web servers). This destination filename is the one that the remote client specified. You do not have to listen to this client. You could, for example, copy all uploaded files to a special uploads directory.
As long as support for the "URL fopen wrapper" is enabled when you configure PHP (which it is unless you explicitly pass the --disable-url-fopen-wrapper flag to configure), you can use HTTP and FTP URLs with most functions that take a filename as a parameter, including the require() and include() statements.
For example, you can use this to open a file on a remote web server, parse the output for the data you want, and then use that data in a database query, or simply to output it in a style matching the rest of your website.
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Example 20-1. Getting the title of a remote page
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You can also write to files on an FTP as long you connect as a user with the correct access rights, and the file doesn't exist already. To connect as a user other than 'anonymous', you need to specify the username (and possibly password) within the URL, such as 'ftp://user:password@ftp.example.com/path/to/file'. (You can use the same sort of syntax to access files via HTTP when they require Basic authentication.)
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Example 20-2. Storing data on a remote server
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Note: You might get the idea from the example above to use this technique to write to a remote log, but as mentioned above, you can only write to a new file using the URL fopen() wrappers. To do distributed logging like that, you should take a look at syslog().
Note: The following applies to 3.0.7 and later.
Internally in PHP a connection status is maintained. There are 3 possible states:
0 - NORMAL
1 - ABORTED
2 - TIMEOUT
When a PHP script is running normally the NORMAL state, is active. If the remote client disconnects the ABORTED state flag is turned on. A remote client disconnect is usually caused by the user hitting his STOP button. If the PHP-imposed time limit (see set_time_limit()) is hit, the TIMEOUT state flag is turned on.
You can decide whether or not you want a client disconnect to cause your script to be aborted. Sometimes it is handy to always have your scripts run to completion even if there is no remote browser receiving the output. The default behaviour is however for your script to be aborted when the remote client disconnects. This behaviour can be set via the ignore_user_abort php3.ini directive as well as through the corresponding php3_ignore_user_abort Apache .conf directive or with the ignore_user_abort() function. If you do not tell PHP to ignore a user abort and the user aborts, your script will terminate. The one exception is if you have registered a shutdown function using register_shutdown_function(). With a shutdown function, when the remote user hits his STOP button, the next time your script tries to output something PHP will detect that the connection has been aborted and the shutdown function is called. This shutdown function will also get called at the end of your script terminating normally, so to do something different in case of a client diconnect you can use the connection_aborted() function. This function will return true if the connection was aborted.
Your script can also be terminated by the built-in script timer. The default timeout is 30 seconds. It can be changed using the max_execution_time php3.ini directive or the corresponding php3_max_execution_time Apache .conf directive as well as with the set_time_limit() function. When the timer expires the script will be aborted and as with the above client disconnect case, if a shutdown function has been registered it will be called. Within this shutdown function you can check to see if a timeout caused the shutdown function to be called by calling the connection_timeout() function. This function will return true if a timeout caused the shutdown function to be called.
One thing to note is that both the ABORTED and the TIMEOUT states can be active at the same time. This is possible if you tell PHP to ignore user aborts. PHP will still note the fact that a user may have broken the connection, but the script will keep running. If it then hits the time limit it will be aborted and your shutdown function, if any, will be called. At this point you will find that connection_timeout() and connection_aborted() return true. You can also check both states in a single call by using the connection_status(). This function returns a bitfield of the active states. So, if both states are active it would return 3, for example.
Persistent connections are SQL links that do not close when the execution of your script ends. When a persistent connection is requested, PHP checks if there's already an identical persistent connection (that remained open from earlier) - and if it exists, it uses it. If it does not exist, it creates the link. An 'identical' connection is a connection that was opened to the same host, with the same username and the same password (where applicable).
People who aren't thoroughly familiar with the way web servers work and distribute the load may mistake persistent connects for what they're not. In particular, they do not give you an ability to open 'user sessions' on the same SQL link, they do not give you an ability to build up a transaction efficently, and they don't do a whole lot of other things. In fact, to be extremely clear about the subject, persistent connections don't give you any functionality that wasn't possible with their non-persistent brothers.
Why?
This has to do with the way web servers work. There are three ways in which your web server can utilize PHP to generate web pages.
The first method is to use PHP as a CGI "wrapper". When run this way, an instance of the PHP interpreter is created and destroyed for every page request (for a PHP page) to your web server. Because it is destroyed after every request, any resources that it acquires (such as a link to an SQL database server) are closed when it is destroyed. In this case, you do not gain anything from trying to use persistent connections -- they simply don't persist.
The second, and most popular, method is to run PHP as a module in a multiprocess web server, which currently only includes Apache. A multiprocess server typically has one process (the parent) which coordinates a set of processes (its children) who actually do the work of serving up web pages. When each request comes in from a a client, it is handed off to one of the children that is not already serving another client. This means that when the same client makes a second request to the server, it may be serviced by a different child process than the first time. What a persistent connection does for you in this case it make it so each child process only needs to connect to your SQL server the first time that it serves a page that makes us of such a connection. When another page then requires a connection to the SQL server, it can reuse the connection that child established earlier.
The last method is to use PHP as a plug-in for a multithreaded web server. Currently this is only theoretical -- PHP does not yet work as a plug-in for any multithreaded web servers. Work is progressing on support for ISAPI, WSAPI, and NSAPI (on Windows), which will all allow PHP to be used as a plug-in on multithreaded servers like Netscape FastTrack, Microsoft's Internet Information Server (IIS), and O'Reilly's WebSite Pro. When this happens, the behavior will be essentially the same as for the multiprocess model described before.
If persistent connections don't have any added functionality, what are they good for?
The answer here is extremely simple -- efficiency. Persistent connections are good if the overhead to create a link to your SQL server is high. Whether or not this overhead is really high depends on many factors. Like, what kind of database it is, whether or not it sits on the same computer on which your web server sits, how loaded the machine the SQL server sits on is and so forth. The bottom line is that if that connection overhead is high, persistent connections help you considerably. They cause the child process to simply connect only once for its entire lifespan, instead of every time it processes a page that requires connecting to the SQL server. This means that for every child that opened a persistent connection will have its own open persistent connection to the server. For example, if you had 20 different child processes that ran a script that made a persistent connection to your SQL server, you'd have 20 different connections to the SQL server, one from each child.
Note, however, that this can have some drawbacks if you are using a database with connection limits that are exceeded by persistant child connections. If your database has a limit of 16 simultaneous connections, and in the course of a busy server session, 17 child threads attempt to connect, one will not be able to. If there are bugs in your scripts which do not allow the connections to shut down (such as infinite loops), a database with only 32 connections may be rapidly swamped. Check your database documentation for information on handling abandoned or idle connections.
An important summary. Persistent connections were designed to have one-to-one mapping to regular connections. That means that you should always be able to replace persistent connections with non-persistent connections, and it won't change the way your script behaves. It may (and probably will) change the efficiency of the script, but not its behavior!
(PHP3 >= 3.0.4, PHP4 )
apache_lookup_uri -- Perform a partial request for the specified URI and return all info about itclass apache_lookup_uri (string filename)
This performs a partial request for a URI. It goes just far enough to obtain all the important information about the given resource and returns this information in a class. The properties of the returned class are:
| status |
| the_request |
| status_line |
| method |
| content_type |
| handler |
| uri |
| filename |
| path_info |
| args |
| boundary |
| no_cache |
| no_local_copy |
| allowed |
| send_bodyct |
| bytes_sent |
| byterange |
| clength |
| unparsed_uri |
| mtime |
| request_time |
Note: Apache_lookup_uri() only works when PHP is installed as an Apache module.
string apache_note
(string note_name [, string note_value])
Apache_note() is an Apache-specific function which gets and sets values in a request's notes table. If called with one argument, it returns the current value of note note_name. If called with two arguments, it sets the value of note note_name to note_value and returns the previous value of note note_name.
array getallheaders
(void)
This function returns an associative array of all the HTTP headers in the current request.
Note: You can also get at the value of the common CGI variables by reading them from the environment, which works whether or not you are using PHP as an Apache module. Use phpinfo() to see a list of all of the environment variables defined this way.
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Example 1. getallheaders() Example
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This example will display all the request headers for the current request.
Note: Getallheaders() is currently only supported when PHP runs as an Apache module.
int virtual (string
filename)
Virtual() is an Apache-specific function which is equivalent to <!--#include virtual...--> in mod_include. It performs an Apache sub-request. It is useful for including CGI scripts or .shtml files, or anything else that you would parse through Apache. Note that for a CGI script, the script must generate valid CGI headers. At the minimum that means it must generate a Content-type header. For PHP files, you need to use include() or require(); virtual() cannot be used to include a document which is itself a PHP file.
These functions allow you to interact with and manipulate arrays in various ways. Arrays are essential for storing, managing, and operating on sets of variables.
Simple and multi-dimensional arrays are supported, and may be either user created or created by another function. There are specific database handling functions for populating arrays from database queries, and several functions return arrays.
array array ([mixed
...])
Returns an array of the parameters. The parameters can be given an index with the => operator.
Note: Array() is a language construct used to represent literal arrays, and not a regular function.
The following example demonstrates how to create a two-dimensional array, how to specify keys for associative arrays, and how to skip-and-continue numeric indices in normal arrays.
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Example 1. Array() example
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See also: list().
array array_count_values (array input)
Array_count_values() returns an array using the values of the input array as keys and their frequency in input as values.
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Example 1. Array_count_values() example
|
array array_diff
(array array1, array array2 [, array ...])
Array_diff() returns an array containing all the values of array1 that are not present in any of the other arguments. Note that keys are preserved.
|
Example 1. Array_diff() example
|
This makes $result have array ("blue");
See also array_intersect().
array array_flip
(array trans)
Array_flip() returns an array in flip order.
|
Example 1. Array_flip() example
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array array_intersect
(array array1, array array2 [, array ...])
Array_intersect() returns an array containing all the values of array1 that are present in all the arguments. Note that keys are preserved.
|
Example 1. Array_intersect() example
|
This makes $result have array ("a" => "green", "red");
See also array_diff().
array array_keys
(array input [, mixed search_value])
Array_keys() returns the keys, numeric and string, from the input array.
If the optional search_value is specified, then only the keys for that value are returned. Otherwise, all the keys from the input are returned.
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Example 1. Array_keys() example
|
See also array_values().
array array_merge
(array array1, array array2 [, array ...])
Array_merge() merges the elements of two or more arrays together so that the values of one are appended to the end of the previous one. It returns the resulting array.
If the input arrays have the same string keys, then the later value for that key will overwrite the previous one. If, however, the arrays have the same numeric key, the later value will not overwrite the original value, but will be appended.
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Example 1. array_merge() example
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Resulting array will be array("color" => "green", 2, 4, "a", "b", "shape" => "trapezoid", 4).
See also array_merge_recursive().
array array_merge_recursive (array array1, array array2 [,
array ...])
Array_merge_recursive() merges the elements of two or more arrays together so that the values of one are appended to the end of the previous one. It returns the resulting array.
If the input arrays have the same string keys, then the values for these keys are merged together into an array, and this is done recursively, so that if one of the values is an array itself, the function will merge it with a corresponding entry in another array too. If, however, the arrays have the same numeric key, the later value will not overwrite the original value, but will be appended.
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Example 1. Array_merge_recursive() example
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Resulting array will be array ("color" => array ("favorite" => array ("red", "green"), "blue"), 5, 10).
See also array_merge().
bool array_multisort
(array ar1 [, mixed arg [, mixed ... [, array ...]]])
Array_multisort() can be used to sort several arrays at once or a multi-dimensional array according by one of more dimensions. It maintains key association when sorting.
The input arrays are treated as columns of a table to be sorted by rows - this resembles the functionality of SQL ORDER BY clause. The first array is the primary one to sort by. The rows (values) in that array that compare the same are sorted by the next input array, and so on.
The argument structure of this function is a bit unusual, but flexible. The very first argument has to be an array. Subsequently, each argument can be either an array or a sorting flag from the following lists.
Sorting order flags:
SORT_ASC - sort in ascending order
SORT_DESC - sort in descending order
Sorting type flags:
SORT_REGULAR - compare items normally
SORT_NUMERIC - compare items numerically
SORT_STRING - compare items as strings
No two sorting flags of the same type can be specified after each array. The sortings flags specified after an array argument apply only to that array - they are reset to default SORT_ASC and SORT_REGULAR after before each new array argument.
Returns true on success, false on failure.
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Example 1. Sorting multiple arrays
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In this example, after sorting, the first array will contain 10, "a", 100, 100. The second array will contain 1, 1, 2, "3". The entries in the second array corresponding to the identical entries in the first array (100 and 100) were sorted as well.
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Example 2. Sorting multi-dimensional array
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In this example, after sorting, the first array will contain 10, 100, 100, "a" (it was sorted as strings in ascending order), and the second one will contain 1, 3, "2", 1 (sorted as numbers, in descending order).
array array_pad (array
input, int pad_size, mixed pad_value)
Array_pad() returns a copy of the input padded to size specified by pad_size with value pad_value. If pad_size is positive then the array is padded on the right, if it's negative then on the left. If the absolute value of pad_size is less than or equal to the length of the input then no padding takes place.
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Example 1. Array_pad() example
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mixed array_pop (array
array)
Array_pop() pops and returns the last value of the array, shortening the array by one element.
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Example 1. Array_pop() example
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After this, $stack has only 2 elements: "orange" and "apple", and $fruit has "raspberry".
See also array_push(), array_shift(), and array_unshift().
int array_push (array
array, mixed var [, mixed ...])
Array_push() treats array as a stack, and pushes the passed variables onto the end of array. The length of array increases by the number of variables pushed. Has the same effect as:
$array[] = $var;
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Returns the new number of elements in the array.
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Example 1. Array_push() example
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This example would result in $stack having 4 elements: 1, 2, "+", and 3.
See also: array_pop(), array_shift(), and array_unshift().
mixed array_rand
(array input [, int num_req])
Array_rand() is rather useful when you want to pick one or more random entries out of an array. It takes an input array and an optional argument num_req which specifies how many entries you want to pick - if not specified, it defaults to 1.
If you are picking only one entry, array_rand() returns the key for a random entry. Otherwise, it returns an array of keys for the random entries. This is done so that you can pick random keys as well as values out of the array.
Don't forget to call srand() to seed the random number generator.
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Example 1. Array_rand() example
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array array_reverse
(array array)
Array_reverse() takes input array and returns a new array with the order of the elements reversed.
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Example 1. Array_reverse() example
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This makes $result have array (array ("green", "red"), 4.0, "php").
mixed array_shift
(array array)
Array_shift() shifts the first value of the array off and returns it, shortening the array by one element and moving everything down.
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Example 1. Array_shift() example
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This would result in $args having one element "-f" left, and $opt being "-v".
See also array_unshift(), array_push(), and array_pop().
array array_slice
(array array, int offset [, int length])
Array_slice() returns a sequence of elements from the array specified by the offset and length parameters.
If offset is positive, the sequence will start at that offset in the array. If offset is negative, the sequence will start that far from the end of the array.
If length is given and is positive, then the sequence will have that many elements in it. If length is given and is negative then the sequence will stop that many elements from the end of the array. If it is omitted, then the sequence will have everything from offset up until the end of the array.
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Example 1. Array_slice() examples
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See also array_splice().
array array_splice
(array input, int offset [, int length [, array replacement]])
Array_splice() removes the elements designated by offset and length from the input array, and replaces them with the elements of the replacement array, if supplied.
If offset is positive then the start of removed portion is at that offset from the beginning of the input array. If offset is negative then it starts that far from the end of the input array.
If length is omitted, removes everything from offset to the end of the array. If length is specified and is positive, then that many elements will be removed. If length is specified and is negative then the end of the removed portion will be that many elements from the end of the array. Tip: to remove everything from offset to the end of the array when replacement is also specified, use count($input) for length.
If replacement array is specified, then the removed elements are replaced with elements from this array. If offset and length are such that nothing is removed, then the elements from the replacement array are inserted in the place specified by the offset. Tip: if the replacement is just one element it is not necessary to put array() around it, unless the element is an array itself.
The following equivalences hold:
array_push ($input, $x, $y) array_splice ($input, count ($input), 0,
array ($x, $y))
array_pop ($input) array_splice ($input, -1)
array_shift ($input) array_splice ($input, 0, 1)
array_unshift ($input, $x, $y) array_splice ($input, 0, 0, array ($x, $y))
$a[$x] = $y array_splice ($input, $x, 1, $y)
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Returns the array consisting of removed elements.
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Example 1. Array_splice() examples
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See also array_slice().
array array_unique
(array array)
Array_unique() takes input array and returns a new array without duplicate values. Note that keys are preserved.
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Example 1. Array_unique() example
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This makes $result have array ("a" => "green", "red", "blue");
int array_unshift
(array array, mixed var [, mixed ...])
Array_unshift() prepends passed elements to the front of the array. Note that the list of elements is prepended as a whole, so that the prepended elements stay in the same order.
Returns the new number of elements in the array.
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Example 1. Array_unshift() example
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This would result in $queue having 5 elements: "p4", "p5", "p6", "p1", and "p3".
See also array_shift(), array_push(), and array_pop().
array array_values
(array input)
Array_values() returns all the values from the input array.
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Example 1. Array_values() example
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int array_walk (array
arr, string func, mixed userdata)
Applies the function named by func to each element of arr. func will be passed array value as the first parameter and array key as the second parameter. If userdata is supplied, it will be passed as the third parameter to the user function.
If func requires more than two or three arguments, depending on userdata, a warning will be generated each time array_walk() calls func. These warnings may be suppressed by prepending the '@' sign to the array_walk() call, or by using error_reporting().
Note: If func needs to be working with the actual values of the array, specify that the first parameter of func should be passed by reference. Then any changes made to those elements will be made in the array itself.
Note: Passing the key and userdata to func was added in 4.0.
In PHP 4 reset() needs to be called as necessary since array_walk() does not reset the array by default.
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Example 1. Array_walk() example
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void arsort (array
array [, int sort_flags])
This function sorts an array such that array indices maintain their correlation with the array elements they are associated with. This is used mainly when sorting associative arrays where the actual element order is significant.
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Example 1. Arsort() example
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This example would display:
fruits[a] = orange
fruits[d] = lemon
fruits[b] = banana
fruits[c] = apple
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The fruits have been sorted in reverse alphabetical order, and the index associated with each element has been maintained.
You may modify the behavior of the sort using the optional parameter sort_flags, for details see sort().
void asort (array
array [, int sort_flags])
This function sorts an array such that array indices maintain their correlation with the array elements they are associated with. This is used mainly when sorting associative arrays where the actual element order is significant.
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Example 1. Asort() example
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This example would display:
fruits[c] = apple
fruits[b] = banana
fruits[d] = lemon
fruits[a] = orange
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The fruits have been sorted in alphabetical order, and the index associated with each element has been maintained.
You may modify the behavior of the sort using the optional parameter sort_flags, for details see sort().
array compact (mixed
varname [, mixed ...])
Compact() takes a variable number of parameters. Each parameter can be either a string containing the name of the variable, or an array of variable names. The array can contain other arrays of variable names inside it; compact() handles it recursively.
For each of these, compact() looks for a variable with that name in the current symbol table and adds it to the output array such that the variable name becomes the key and the contents of the variable become the value for that key. In short, it does the opposite of extract(). It returns the output array with all the variables added to it.
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Example 1. Compact() example
After this, $result will be array ("event" => "SIGGRAPH", "city" => "San Francisco", "state" => "CA"). |
See also extract().
int count (mixed
var)
Returns the number of elements in var, which is typically an array (since anything else will have one element).
Returns 1 if the variable is not an array.
Returns 0 if the variable is not set.
| Warning |
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Count() may return 0 for a variable that isn't set, but it may also return 0 for a variable that has been initialized with an empty array. Use isset() to test if a variable is set. |
See also: sizeof(), isset(), and is_array().
mixed current (array
array)
Every array has an internal pointer to its "current" element, which is initialized to the first element inserted into the array.
The current() function simply returns the array element that's currently being pointed by the internal pointer. It does not move the pointer in any way. If the internal pointer points beyond the end of the elements list, current() returns false.
| Warning |
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If the array contains empty elements (0 or "", the empty string) then this function will return false for these elements as well. This makes it impossible to determine if you are really at the end of the list in such an array using current(). To properly traverse an array that may contain empty elements, use the each() function. |
array each (array
array)
Returns the current key and value pair from the array array and advances the array cursor. This pair is returned in a four-element array, with the keys 0, 1, key, and value. Elements 0 and key contain the key name of the array element, and 1 and value contain the data.
If the internal pointer for the array points past the end of the array contents, each() returns false.
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Example 1. Each() examples
$bar now contains the following key/value pairs:
$bar now contains the following key/value pairs:
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Each() is typically used in conjunction with list() to traverse an array; for instance, $HTTP_POST_VARS:
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Example 2. Traversing $HTTP_POST_VARS with each()
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After each() has executed, the array cursor will be left on the next element of the array, or on the last element if it hits the end of the array.
See also key(), list(), current(), reset(), next(), and prev().
void extract (array
var_array [, int extract_type [, string prefix]])
This function is used to import variables from an array into the current symbol table. It takes associative array var_array and treats keys as variable names and values as variable values. For each key/value pair it will create a variable in the current symbol table, subject to extract_type and prefix parameters.
Extract() checks for colissions with existing variables. The way collisions are treated is determined by extract_type. It can be one of the following values:
If there is a collision, overwrite the existing variable.
If there is a collision, don't overwrite the existing variable.
If there is a collision, prefix the new variable with prefix.
Prefix all variables with prefix.
If extract_type is not specified, it is assumed to be EXTR_OVERWRITE.
Note that prefix is only required if extract_type is EXTR_PREFIX_SAME or EXTR_PREFIX_ALL.
Extract() checks each key to see if it constitues a valid variable name, and if it does only then does it proceed to import it.
A possible use for extract is to import into symbol table variables contained in an associative array returned by wddx_deserialize().
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Example 1. Extract() example
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The above example will produce:
blue, large, sphere, medium
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The $size wasn't overwritten, becaus we specified EXTR_PREFIX_SAME, which resulted in $wddx_size being created. If EXTR_SKIP was specified, then $wddx_size wouldn't even have been created. EXTR_OVERWRITE would have cause $size to have value "medium", and EXTR_PREFIX_ALL would result in new variables being named $wddx_color, $wddx_size, and $wddx_shape.
bool in_array (mixed needle, array
haystack)
Searches haystack for needle and returns true if it is found in the array, false otherwise.
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Example 1. In_array() example
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int krsort (array
array [, int sort_flags])
Sorts an array by key in reverse order, maintaining key to data correlations. This is useful mainly for associative arrays.
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Example 1. Krsort() example
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This example would display:
fruits[d] = lemon
fruits[c] = apple
fruits[b] = banana
fruits[a] = orange
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You may modify the behavior of the sort using the optional parameter sort_flags, for details see sort().
int ksort (array array
[, int sort_flags])
Sorts an array by key, maintaining key to data correlations. This is useful mainly for associative arrays.
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Example 1. Ksort() example
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This example would display:
fruits[a] = orange
fruits[b] = banana
fruits[c] = apple
fruits[d] = lemon
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You may modify the behavior of the sort using the optional parameter sort_flags, for details see sort().
void list(...);
Like array(), this is not really a function, but a language construct. list() is used to assign a list of variables in one operation.
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Example 1. List() example
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mixed next (array
array)
Returns the array element in the next place that's pointed by the internal array pointer, or false if there are no more elements.
Next() behaves like current(), with one difference. It advances the internal array pointer one place forward before returning the element. That means it returns the next array element and advances the internal array pointer by one. If advancing the internal array pointer results in going beyond the end of the element list, next() returns false.
| Warning |
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If the array contains empty elements, or elements that have a key value of 0 then this function will return false for these elements as well. To properly traverse an array which may contain empty elements or elements with key values of 0 see the each() function. |
mixed prev (array
array)
Returns the array element in the previous place that's pointed by the internal array pointer, or false if there are no more elements.
| Warning |
|
If the array contains empty elements then this function will return false for these elements as well. To properly traverse an array which may contain empty elements see the each() function. |
Prev() behaves just like next(), except it rewinds the internal array pointer one place instead of advancing it.
array range (int low,
int high)
Range() returns an array of integers from low to high, inclusive.
See shuffle() for an example of its use.
mixed reset (array
array)
Reset() rewinds array's internal pointer to the first element.
Reset() returns the value of the first array element.
void rsort (array
array [, int sort_flags])
This function sorts an array in reverse order (highest to lowest).
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Example 1. Rsort() example
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This example would display:
fruits[0] = orange
fruits[1] = lemon
fruits[2] = banana
fruits[3] = apple
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The fruits have been sorted in reverse alphabetical order.
You may modify the behavior of the sort using the optional parameter sort_flags, for details see sort().
void shuffle (array
array)
This function shuffles (randomizes the order of the elements in) an array.
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Example 1. Shuffle() example
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See also arsort(), asort(), ksort(), rsort(), sort() and usort().
void sort (array array
[, int sort_flags])
This function sorts an array. Elements will be arranged from lowest to highest when this function has completed.
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Example 1. Sort() example
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This example would display:
fruits[0] = apple
fruits[1] = banana
fruits[2] = lemon
fruits[3] = orange
|
The fruits have been sorted in alphabetical order.
The optional second parameter sort_flags may be used to modify the sorting behavior using theese valies:
Sorting type flags:
SORT_REGULAR - compare items normally
SORT_NUMERIC - compare items numerically
SORT_STRING - compare items as strings
(PHP3 >= 3.0.4, PHP4 )
uasort -- Sort an array with a user-defined comparison function and maintain index associationvoid uasort (array
array, function cmp_function)
This function sorts an array such that array indices maintain their correlation with the array elements they are associated with. This is used mainly when sorting associative arrays where the actual element order is significant. The comparison function is user-defined.
See also: usort(), uksort(), sort(), asort(), arsort(), ksort() and rsort().
void uksort (array
array, function cmp_function)
This function will sort the keys of an array using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function.
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Example 1. Uksort() example
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This example would display:
20: twenty
10: ten
4: four
3: three
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See also: usort(), uasort(), sort(), asort(), arsort(), ksort() and rsort().
void usort (array
array, string cmp_function)
This function will sort an array by its values using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function.
The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second. If two members compare as equal, their order in the sorted array is undefined.
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Example 1. Usort() example
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This example would display:
0: 6
1: 5
2: 3
3: 2
4: 1
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Note: Obviously in this trivial case the rsort() function would be more appropriate.
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Example 2. Usort() example using multi-dimensional array
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When sorting a multi-dimensional array, $a and $b contain references to the first index of the array.
This example would display:
$fruits[0]: apples
$fruits[1]: grapes
$fruits[2]: lemons
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| Warning |
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The underlying quicksort function in some C libraries (such as on Solaris systems) may cause PHP to crash if the comparison function does not return consistent values. |
See also: uasort(), uksort(), sort(), asort(), arsort(), ksort() and rsort().
The aspell() functions allows you to check the spelling on a word and offer suggestions.
Note: aspell works only with very old (up to .27.* or so) versions of aspell library. Neither this module, nor those versions of aspell library are supported any longer. If you want to use spell-checking capabilities in php, use pspell instead. It uses pspell library and works with newer versions of aspell.
You need the aspell library, available from: http://aspell.sourceforge.net/.
int aspell_new (string
master, string personal)
Aspell_new() opens up a new dictionary and returns the dictionary link identifier for use in other aspell functions.
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Example 1. Aspell_new()
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boolean aspell_check
(int dictionary_link, string word)
Aspell_check() checks the spelling of a word and returns true if the spelling is correct, false if not.
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Example 1. Aspell_check()
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(PHP3 >= 3.0.7, PHP4 )
aspell_check-raw -- Check a word without changing its case or trying to trim itboolean aspell_check_raw (int dictionary_link, string
word)
Aspell_check_raw() checks the spelling of a word, without changing its case or trying to trim it in any way and returns true if the spelling is correct, false if not.
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Example 1. Aspell_check_raw()
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array aspell_suggest
(int dictionary_link, string word)
Aspell_suggest() returns an array of possible spellings for the given word.
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Example 1. Aspell_suggest()
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string bcadd (string
left operand, string right operand [, int scale])
Adds the left operand to the right operand and returns the sum in a string. The optional scale parameter is used to set the number of digits after the decimal place in the result.
See also bcsub().
int bccomp (string
left operand, string right operand [, int scale])
Compares the left operand to the right operand and returns the result as an integer. The optional scale parameter is used to set the number of digits after the decimal place which will be used in the comparion. The return value is 0 if the two operands are equal. If the left operand is larger than the right operand the return value is +1 and if the left operand is less than the right operand the return value is -1.
string bcdiv (string
left operand, string right operand [, int scale])
Divides the left operand by the right operand and returns the result. The optional scale sets the number of digits after the decimal place in the result.
See also bcmul().
string bcmod (string
left operand, string modulus)
Get the modulus of the left operand using modulus.
See also bcdiv().
string bcmul (string
left operand, string right operand [, int scale])
Multiply the left operand by the right operand and returns the result. The optional scale sets the number of digits after the decimal place in the result.
See also bcdiv().
string bcpow (string
x, string y [, int scale])
Raise x to the power y. The optional scale can be used to set the number of digits after the decimal place in the result.
See also bcsqrt().
string bcscale (int
scale)
This function sets the default scale parameter for all subsequent bc math functions that do not explicitly specify a scale parameter.
string bcsqrt (string
operand, int scale)
Return the square root of the operand. The optional scale parameter sets the number of digits after the decimal place in the result.
See also bcpow().
string bcsub (string
left operand, string right operand [, int scale])
Subtracts the right operand from the left operand and returns the result in a string. The optional scale parameter is used to set the number of digits after the decimal place in the result.
See also bcadd().
The calendar functions are only available if you have compiled the calendar extension in dl/calendar. Read dl/README for instructions on using it.
The calendar extension presents a series of functions to simplify converting between different calendar formats. The intermediary or standard it is based on is the Julian Day Count. The Julian Day Count is a count of days starting way earlier than any date most people would need to track (somewhere around 4000bc). To convert between calendar systems, you must first convert to Julian Day Count, then to the calendar system of your choice. Julian Day Count is very different from the Julian Calendar! For more information on calendar systems visit http://genealogy.org/~scottlee/cal-overview.html. Excerpts from this page are included in these instructions, and are in quotes.
string jdtogregorian
(int julianday)
Converts Julian Day Count to a string containing the Gregorian date in the format of "month/day/year".
int gregoriantojd (int
month, int day, int year)
Valid Range for Gregorian Calendar 4714 B.C. to 9999 A.D.
Although this software can handle dates all the way back to 4714 B.C., such use may not be meaningful. The Gregorian calendar was not instituted until October 15, 1582 (or October 5, 1582 in the Julian calendar). Some countries did not accept it until much later. For example, Britain converted in 1752, The USSR in 1918 and Greece in 1923. Most European countries used the Julian calendar prior to the Gregorian.
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Example 1. Calendar functions
|
string jdtojulian (int
julianday)
Converts Julian Day Count to a string containing the Julian Calendar Date in the format of "month/day/year".
int juliantojd (int
month, int day, int year)
Valid Range for Julian Calendar 4713 B.C. to 9999 A.D.
Although this software can handle dates all the way back to 4713 B.C., such use may not be meaningful. The calendar was created in 46 B.C., but the details did not stabilize until at least 8 A.D., and perhaps as late at the 4th century. Also, the beginning of a year varied from one culture to another - not all accepted January as the first month.
int jewishtojd (int
month, int day, int year)
Valid Range Although this software can handle dates all the way back to the year 1 (3761 B.C.), such use may not be meaningful.
The Jewish calendar has been in use for several thousand years, but in the early days there was no formula to determine the start of a month. A new month was started when the new moon was first observed.
string jdtofrench (int
month, int day, int year)
Converts a Julian Day Count to the French Republican Calendar.
(PHP3 , PHP4 )
FrenchToJD -- Converts a date from the French Republican Calendar to a Julian Day Countint frenchtojd (int
month, int day, int year)
Converts a date from the French Republican Calendar to a Julian Day Count.
These routines only convert dates in years 1 through 14 (Gregorian dates 22 September 1792 through 22 September 1806). This more than covers the period when the calendar was in use.
string jdmonthname
(int julianday, int mode)
Returns a string containing a month name. mode tells this function which calendar to convert the Julian Day Count to, and what type of month names are to be returned.
Table 1. Calendar modes
| Mode | Meaning |
|---|---|
| 0 | Gregorian - abbreviated |
| 1 | Gregorian |
| 2 | Julian - abbreviated |
| 3 | Julian |
| 4 | Jewish |
| 5 | French Republican |
mixed jddayofweek (int
julianday, int mode)
Returns the day of the week. Can return a string or an int depending on the mode.
Table 1. Calendar week modes
| Mode | Meaning |
|---|---|
| 0 | Returns the day number as an int (0=sunday, 1=monday, etc) |
| 1 | Returns string containing the day of week (english-gregorian) |
| 2 | Returns a string containing the abbreviated day of week (english-gregorian) |
(PHP3 >= 3.0.9, PHP4 >= 4.0RC2)
easter_date -- Get UNIX timestamp for midnight on Easter of a given yearint easter_date (int
year)
Returns the UNIX timestamp corresponding to midnight on Easter of the given year. If no year is specified, the current year is assumed.
Warning: This function will generate a warning if the year is outside of the range for UNIX timestamps (i.e. before 1970 or after 2037).
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Example 1. easter_date() example
|
The date of Easter Day was defined by the Council of Nicaea in AD325 as the Sunday after the first full moon which falls on or after the Spring Equinox. The Equinox is assumed to always fall on 21st March, so the calculation reduces to determining the date of the full moon and the date of the following Sunday. The algorithm used here was introduced around the year 532 by Dionysius Exiguus. Under the Julian Calendar (for years before 1753) a simple 19-year cycle is used to track the phases of the Moon. Under the Gregorian Calendar (for years after 1753 - devised by Clavius and Lilius, and introduced by Pope Gregory XIII in October 1582, and into Britain and its then colonies in September 1752) two correction factors are added to make the cycle more accurate.
(The code is based on a C program by Simon Kershaw, <webmaster@ely.anglican.org>)
See easter_days() for calculating Easter before 1970 or after 2037.
(PHP3 >= 3.0.9, PHP4 >= 4.0RC2)
easter_days -- Get number of days after March 21 on which Easter falls for a given yearint easter_days (int
year)
Returns the number of days after March 21 on which Easter falls for a given year. If no year is specified, the current year is assumed.
This function can be used instead of easter_date() to calculate Easter for years which fall outside the range of UNIX timestamps (i.e. before 1970 or after 2037).
|
Example 1. Easter_date() example
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The date of Easter Day was defined by the Council of Nicaea in AD325 as the Sunday after the first full moon which falls on or after the Spring Equinox. The Equinox is assumed to always fall on 21st March, so the calculation reduces to determining the date of the full moon and the date of the following Sunday. The algorithm used here was introduced around the year 532 by Dionysius Exiguus. Under the Julian Calendar (for years before 1753) a simple 19-year cycle is used to track the phases of the Moon. Under the Gregorian Calendar (for years after 1753 - devised by Clavius and Lilius, and introduced by Pope Gregory XIII in October 1582, and into Britain and its then colonies in September 1752) two correction factors are added to make the cycle more accurate.
(The code is based on a C program by Simon Kershaw, <webmaster@ely.anglican.org>)
See also easter_date().
int unixtojd ([int
timestamp])
Return the Julian Day for a UNIX timestamp (seconds since 1.1.1970), or for the current day if no timestamp is given.
See also jdtounix().
Note: This function is only available in PHP versions after PHP4RC1.
int jdtounix (int
jday)
This function will return a UNIX timestamp corresponding to the Julian Day given in jday or false if jday is not inside the UNIX epoch (Gregorian years between 1970 and 2037 or 2440588 <= jday <= 2465342 )
See also jdtounix().
Note: This function is only available in PHP versions after PHP4RC1.
These functions interface the CCVS API, allowing you to directly work with CCVS from your PHP scripts. CCVS is RedHat's solution to the "middle-man" in credit card processing. It lets you directly address the credit card clearing houses via your *nix box and a modem. Using the CCVS module for PHP, you can process credit cards directly through CCVS via your PHP Scripts. The following references will outline the process.
To enable CCVS Support in PHP, first verify your CCVS installation directory. You will then need to configure PHP with the --with-ccvs option. If you use this option without specifying the path to your CCVS installation, PHP Will attempt to look in the default CCVS Install location (/usr/local/ccvs). If CCVS is in a non-standard location, run configure with: --with-ccvs=$ccvs_path, where $ccvs_path is the path to your CCVS installation. Please note that CCVS support requires that $ccvs_path/lib and $ccvs_path/include exist, and include cv_api.h under the include directory and libccvs.a under the lib directory.
Additionally, a ccvsd process will need to be running for the configurations you intend to use in your PHP scripts. You will also need to make sure the PHP Processes are running under the same user as your CCVS was installed as (e.g. if you installed CCVS as user 'ccvs', your PHP processes must run as 'ccvs' as well.)
Additional information about CCVS can be found at http://www.redhat.com/products/ccvs.
This documentation section is being worked on. Until then, RedHat maintains slightly outdated but still useful documentation at http://www.redhat.com/products/ccvs/support/CCVS3.3docs/ProgPHP.html.
These functions are only available on the Windows version of PHP. These functions have been added in PHP4.
mixed com_invoke
(resource object, string function_name [, mixed function parameters,
...])
void com_propset
(resource object, string property, mixed value)
This function is an alias for com_propput().
These functions allow you to obtain information about classes and instance objects. You can obtain the name of the class to which a object belongs, as well as its member properties and methods. Using these functions, you can find out not only the class membership of an object, but also its parentage (i.e. what class is the object class extending).
In this example, we first define a base class and an extension of the class. The base class describes a general vegetable, whether it is edible or not and what is its color. The subclass Spinach adds a method to cook it and another to find out if it is cooked.
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Example 1. classes.inc
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We then instantiate 2 objects from these classes and print out information about them, including their class parentage. We also define some utility functions, mainly to have a nice printout of the variables.
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Example 2. test_script.php
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One important thing to note in the example above is that the object $leafy is an instance of the class Spinach which is a subclass of Vegetable, therefore the last part of the script above will output:
[...] Parentage: Object leafy does not belong to a subclass of Spinach Object leafy belongs to class spinach a subclass of Vegetable |
string get_class
(object obj)
This function returns the name of the class of which the object obj is an instance.
See also get_parent_class(), is_subclass_of()
string get_parent_class (object obj)
This function returns the name of the parent class to the class of which the object obj is an instance.
See also get_class(), is_subclass_of()
array get_class_methods (string class_name)
This function returns an array of method names defined for the class specified by class_name.
See also get_class_vars(), get_object_vars()
array get_class_vars
(string class_name)
This function will return an array of default properties of the class.
See also get_class_methods(), get_object_vars()
array get_object_vars
(object obj)
This function returns an associative array of object properties for the specified object obj.
See also get_class_methods(), get_class_vars()
(PHP4 >= 4.0b4)
is_subclass_of -- Determines if an object belongs to a subclass of the specified classbool is_subclass_of
(object obj, string superclass)
This function returns true if the object obj, belongs to a class which is a subclass of superclass, false otherwise.
See also get_class(), get_parent_class()
bool class_exists
(string class_name)
This function returns true if the class given by class_name has been defined, false otherwise.
bool method_exists
(object object, string method_name)
This function returns true if the method given by method_name has been defined for the given object, false otherwise.
array get_declared_classes (void)
This function returns an array of the names of the declared classes in the current script.
Note: In PHP 4.0.1pl2, three extra classes are returned at the beginning of the array: stdClass (defined in Zend/zend.c), OverloadedTestClass (defined in ext/standard/basic_functions.c) and Directory (defined in ext/standard/dir.c).
mixed call_user_method
(string method_name, object obj [, mixed parameter [, mixed
...]])
Calls a the method referred by method_name from the user defined obj object. An example of usage is below, where we define a class, instantiate an object and use call_user_method() to call indirectly its print_info method.
<?php
class Country {
var $NAME;
var $TLD;
function Country($name, $tld) {
$this->NAME = $name;
$this->TLD = $tld;
}
function print_info($prestr="") {
echo $prestr."Country: ".$this->NAME."\n";
echo $prestr."Top Level Domain: ".$this->TLD."\n";
}
}
$cntry = new Country("Peru","pe");
echo "* Calling the object method directly\n";
$cntry->print_info();
echo "\n* Calling the same method indirectly\n";
call_user_method ("print_info", $cntry, "\t");
?>
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See also call_user_func().
ClibPDF lets you create PDF documents with PHP. It is available at FastIO but it isn't free software. You should definitely read the licence before you start playing with ClibPDF. If you cannot fullfil the licence agreement consider using pdflib by Thomas Merz, which is also very powerful. ClibPDF functionality and API is similar to Thomas Merz's pdflib but, according to FastIO, ClibPDF is faster and creates smaller documents. This may have changed with the new version 2.0 of pdflib. A simple benchmark (the pdfclock.c example from pdflib 2.0 turned into a php script) actually shows no difference in speed at all. The file size is also similar if compression is turned off. So, try them both and see which one does the job for you.
This documentation should be read alongside the ClibPDF manual since it explains the library in much greater detail.
Many functions in the native ClibPDF and the PHP module, as well as in pdflib, have the same name. All functions except for cpdf_open() take the handle for the document as their first parameter. Currently this handle is not used internally since ClibPDF does not support the creation of several PDF documents at the same time. Actually, you should not even try it, the results are unpredictable. I can't oversee what the consequences in a multi threaded environment are. According to the author of ClibPDF this will change in one of the next releases (current version when this was written is 1.10). If you need this functionality use the pdflib module.
Note: The function cpdf_set_font() has changed since PHP3 to support asian fonts. The encoding parameter is no longer an integer but a string.
One big advantage of ClibPDF over pdflib is the possibility to create the pdf document completely in memory without using temporary files. It also provides the ability to pass coordinates in a predefined unit length. This is a handy feature but can be simulated with pdf_translate().
Most of the functions are fairly easy to use. The most difficult part is probably creating a very simple PDF document at all. The following example should help you get started. It creates a document with one page. The page contains the text "Times-Roman" in an outlined 30pt font. The text is underlined.
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Example 1. Simple ClibPDF Example
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The pdflib distribution contains a more complex example which creates a series of pages with an analog clock. Here is that example converted into PHP using the ClibPDF extension:
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Example 2. pdfclock example from pdflib 2.0 distribution
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void cpdf_global_set_document_limits (int maxpages, int
maxfonts, int maximages, int maxannotations, int maxobjects)
The cpdf_global_set_document_limits() function sets several document limits. This function has to be called before cpdf_open() to take effect. It sets the limits for any document open afterwards.
See also cpdf_open().
void cpdf_set_creator
(string creator)
The cpdf_set_creator() function sets the creator of a pdf document.
See also cpdf_set_subject(), cpdf_set_title(), cpdf_set_keywords().
void cpdf_set_title
(string title)
The cpdf_set_title() function sets the title of a pdf document.
See also cpdf_set_subject(),