PHP

PHP is a scripting language that most of MediaWiki is written in.

You may be looking for:
 * How to become a MediaWiki hacker - introductory information for developers new to PHP
 * Compatibility - version requirement information about MediaWiki
 * PHP configuration - how to edit MediaWiki's PHP-based configuration files
 * Manual:Coding conventions/PHP - formal MediaWiki development guidelines
 * PHP optimisation tips - performance tips when writing PHP code
 * Extension:PhpTags - an extension implementing the concept of Magic expressions with PHP

Obsolote

 * PHP 5.4 - features only available in PHP 5.4 (supported until MW 1.26) or later that are important to MediaWiki developers