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This is a high-level overview of MediaWiki development, including links to the key documents, resources and tools available to MediaWiki developers. It is written for skilled LAMP developers who have experience using MediaWiki.

For an introductory guide to developing MediaWiki, read how to become a MediaWiki hacker.

For help installing or customizing MediaWiki, visit the Sysadmin hub. For help using MediaWiki, visit the User hub.

Overview
MediaWiki is developed in an open source style using the PHP programming language primarily for the LAMP platform. Core development is largely coordinated online.


 * Development discussion happens on various mailing lists and IRC channels. The main developer list is wikitech-l. The main developer IRC channels are #mediawiki and #wikimedia-dev. Read the Developers article to get a sense for who the people on the mailing lists and IRC channels are.


 * Source code is managed using the Git revision control system. Read the Git article for an overview of how the MediaWiki developers use Git. Read the wikitech:Help:Access article if you'd like access.


 * Code review is performed on Gerrit, see this tutorial to get set up with git and gerrit in order to submit patches.


 * Developers extending or interfacing with MediaWiki (instead working on the core code) have several convenient extension points, including the API, the Hooks system and Skins – see the section of this page for an overview.

Key documents


Code, development and style

 * Development policy – an overview of key development policies.


 * Coding conventions – learn how to write PHP code in the MediaWiki style.


 * Security for developers – learn how to help keep MediaWiki secure.


 * Pre-commit checklist – read this checklist before committing code.


 * Code review guide – a guide for reviewers of commits to the MediaWiki source code.


 * Requests for Comment (RfC) – read about or suggest new features for the MediaWiki ecosystem

Debugging and testing

 * Bugs – an overview of bug tracking in the MediaWiki project.


 * How to debug – a guide to debugging MediaWiki.


 * Manual:Errors and Symptoms – an overview of common MediaWiki errors and their correlating symptoms.


 * Selenium Framework – learn to write UI tests for MediaWiki using Selenium.


 * Unit testing – learn to write unit tests for MediaWiki using PHPUnit.


 * Security – security issues are reported to [mailto:security@wikimedia.org security@wikimedia.org].



Architecture

 * Manual:Code – an overview of the key parts of MediaWiki's source code.


 * Database layout – an overview of MediaWiki's database schemas.


 * Global object variables – a partial list of key global variables.


 * Localisation – learn about MediaWiki's internationalisation system.


 * Manual namespace on this wiki – documentation for developers.


 * [//doc.wikimedia.org/mediawiki-core/master/php/html/ MediaWiki Class Reference] – technical documentation generated from the MediaWiki source code. (Note: The class reference is a large, slow-to-load page.)


 * MediaWiki Virtual Library – manuals, guides, collections of selected articles.

Sub-systems

 * API – MediaWiki's API provides direct, high-level access to the data contained in the MediaWiki databases.


 * ContentHandler – MediaWiki's framework for supporting custom types of page content.


 * Database access – an overview of using databases in MediaWiki, including a brief guide to the database abstraction layer.


 * Job queue – MediaWiki's framework for processing long-running tasks asynchronously.


 * Messages API – MediaWiki's framework for providing localized application messages with PHP or JavaScript.

Extending MediaWiki
MediaWiki has been designed to allow for modification without changing the "core code". This makes it easy to update to a new version of MediaWiki without having to manually merge in old extension code changes. There are five main extension points that allow developers to change or extend what MediaWiki can do. The extension points are:


 * API – access the data and metadata of MediaWiki instances through a powerful web API.


 * Hooks – every time a given event happens do something.


 * Parser Functions – create a new command like:


 * Skins – change the look and feel of MediaWiki.


 * Special Pages – add a new special page.


 * Tag Extensions – create a new tag like:

Help for extension developers

 * Manual:Developing extensions – a guide to developing extensions.
 * Project:WikiProject Extensions
 * Extensions FAQ
 * See Category:Extensions, for a list of extensions.
 * Manual:$wgExtensionFunctions – use to defer setup (or run other callbacks) for extensions until after the MediaWiki core is setup.
 * Extension:BoilerPlate - a blank extension template

Help for skin developers

 * Manual:Skinning – instructions on how to create a skin for MediaWiki.
 * Manual:Skin configuration – a guide to configuring skins for a wiki.

Third-party wiki uses

 * Enterprise hub - For Enterprise wikis
 * Academic hub - For Academic wikis