PHP is a widely-used general-purpose scripting language that is especially suited for Web development.
Below you find some additional notes regarding the PHP requirements for Drupal.
PHP from different sources
Drupal is designed to work with PHP as distributed on php.net. Every effort is made to make it work with PHP versions from other sources but this is only done on a best effort basis. In particular, suhosin is known to break certain features and some operating systems move core components into other packages.
The PHP extension for connecting to your chosen database must be installed and enabled. Drupal's currently supported database connectors are: mysql (the original MySQL extension), mysqli (an improved connector for newer MySQL installations), and pgsql (for PostgreSQL). Note: PHP 5.x no longer enables the mysql extension by default. Please read the links above for installing and enabling your chosen connector. Additionally, Drupal 6.x does not provide the option to select the mysql connector if mysqli is enabled in your PHP configuration.
PHP XML extension (for Blog API, Drupal, and Ping modules). This extension is enabled by default in a standard PHP installation; the Windows version of PHP has built-in support for this extension. Enabling the XML extension also enables PHP DOM. DOM is now a systems requirement.
An image library for PHP such as the GD library is needed for image manipulation (resizing user pictures, image and imagecache modules). GD is included with PHP 4.3 and higher and usually enabled by default. ImageMagick is also supported for basic image manipulations in Drupal core but there is much less support from contributed modules.
If you have administrator rights on a Debian/Ubuntu server, and GD is not already available (see your phpinfo) it can usually be installed by running the following command:
sudo apt-get install php5-gd
or on Redhat/Centos:
sudo yum install php-gd
See the ImageMagick install instructions for your platform if you want that.
PHP memory requirements can vary significantly depending on the modules in use on your site. Drupal 6 core requires PHP's memory_limit to be at least 16MB. Drupal 7 core requires 32MB. Warning messages will be shown if the PHP configuration does not meet these requirements. However, while these values may be sufficient for a default Drupal installation, a production site with a number of commonly used modules enabled (CCK, Views etc.) could require 64 MB or more. Some installations may require much more, especially with media-rich implementations. If you are using a hosting service it is important to verify that your host can provide sufficient memory for the set of modules you are deploying or may deploy in the future. (See the Increase PHP memory limit page in the Troubleshooting FAQ for additional information on modifying the PHP memory limit.)
Some of the memory settings are contained in the default .htaccess file that ships with Drupal, so you shouldn't need to set them explicitly. Note, however, that setting PHP configuration options from .htaccess only works under the following conditions:
- With Apache (or a compatible web server)
- If the .htaccess file is actually read, i.e. AllowOverride is not None
- If PHP is installed as an Apache module
In some shared hosting environments, access to these settings is restricted. If you cannot make these changes yourself, please ask your hosting provider to adjust them for you.
- register_globals: off; this is the default value, but some hosts have it enabled
- error_reporting set to E_ALL & ~E_NOTICE. Work is ongoing to change this to E_ALL for Drupal 6 and Drupal 7.
- safe_mode: off. Safe mode may interfere with file and image uploads.
- Tokenizer functions require the tokenizer extension to be enabled. (Read more #357970: Undefined function token_get_all)
- In addition the following settings are recommended:
- session.cache_limiter: nocache
- session.auto_start: 0
- magic_quotes_gpc: off
See the PHP manual for how to change configuration settings for other interfaces to PHP.
If using xdebug, ensure that the xdebug.show_exception_trace value is set to 0, or this could cause Drupal's installer to crash.
Version specific notes on PHP requirements
On Debian libapache2-mod-php5filter may get installed in preference to libapache2-mod-php5 (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=709027). Unfortunately the libapache2-mod-php5filter package has a bug which breaks Drupal - http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=709023
So, make sure you specify to use the libapache2-mod-php5 package instead.
Drupal 8 requires version PHP 5.3.10 or later, with the CURL extension.
Drupal 8 can no longer be installed on hosts with the 'magic_quotes_gpc' or 'magic_quotes_runtime' PHP ini settings turned on; these setting are deprecated in PHP 5.3 and have no effect anymore in PHP 5.4.
- The standard PHP extensions (enabled by default) Hash and JSON are required by Drupal 7.
- Drupal 7 Update manager can install/update modules and themes via SSH if the required libraries have been installed on the server. If you have administrator rights on a Debian/Ubuntu server, and SSH is not already available (see your phpinfo) it can usually be installed by executing:
apt-get install libssh2-php.
- PHP Data Objects (PDO) must be activated for Drupal 7 to install and run correctly. Look in your php.ini. Uncomment (remove the leading semicolon) at line
extension=php_pdo_mysql.dll. In Linux, these would be
extension=pdo_mysql.so. Some Linux distributions may have these extensions by default in files found in the conf.d folder (Ubuntu 12.04:
pdo_mysql.ini). If these lines are not there, you will need to add them. The PECL version of PDO is not compatible with Drupal 7 and cannot be used.
- Drupal 7 may require the time parameter (
max_execution_time) to be at least 30 seconds.
Drupal 7: PHP 5.2.5* or higher (5.3 recommended)
*For Drupal 7, versions of PHP 5.2.4 that include backported security patches also meet the requirements. The PHP version included with Ubuntu 8.04 is the most common example of this.
See the phpinfo() page on Drupal.org to learn how to use phpinfo to get the details of your system. For example, phpinfo will tell you if you have a database already installed and what versions of PHP, MySQL, etc. your system is running. Phpinfo will also tell you what PHP variables are set as well as many other helpful things.
Although PHP 5.3 is supported by Drupal 6, some contributed modules may not be compatible with PHP 5.3, and some PHP 5.3 configurations still show warnings with Drupal 6.14. Work is ongoing to resolve the latter in #360605: PHP 5.3 Compatibility. Most Drupal 6 contributed modules throw E_STRICT errors on PHP 5.3 and many are practically unusuable on 5.4.
Drupal 5 requires PHP 4.4.0 or higher. PHP 5.2 is recommended. Drupal 5.x does not support PHP 5.3