Developer Documentation
Introduction
WordPress believes in keeping it simple, and a lot of thought goes into including new functionality as a part of the "core" WordPress code, in order to keep WordPress fast and lightweight. Still, users often find the need to graft additional functionality onto WordPress to meet their needs. This section of the Codex offers guidelines and references for anyone wishing to modify, extend, or contribute to WordPress.
You may also wish to consult the Developer Documentation FAQ
Programming Code Ahead
In the following articles you may encounter programming terms that are not explained in the usual level of detail required for understanding by non-programmers.
Although the alteration of the downloadable files for WordPress is limited to a few distinct programmers, every WordPress user has the ability to affect change in the core WordPress code, making WordPress highly customizable.
Theme Development
Plugin Development
Writing a Plugin - Best starting place for learning about how to develop plugins Plugin Resources - Comprehensive list of other references for plugin development Plugin API - Hooks, Actions, and Filters to use in your Plugins (version 2.1; has links to older version articles) Function Reference - Complete PHP function reference for WordPress (version 2.1, with links to previous versions) Migrating Plugins and Themes - Contains information on how to upgrade your Plugin so it will work from version to version of WordPress WordPress Coding Standards - General information about coding standards for WordPress development Plugin Submission and Promotion - Once you have written your plugin, here are some hints on distributing it widely Shortcode API - A tutorial and reference for the shortcode API (new in version 2.5)
Contributing to WordPress
Contributing to WordPress - Main starting point if you would like to contribute to core WordPress development, documentation, support, translations, or financial health Automated Testing - Testing WordPress using the automated test suite and how to use the tools and write test cases.
Forums, Lists, and Blogs
Other Information of Interest
Advanced Topics - Annotated list of many articles on advanced WordPress topics Query Overview - Description of the WordPress query process used to find posts and display them Reporting Bugs - Information on reporting and fixing WordPress bugs Using Subversion - Introduction to SVN, the source code repository used by WordPress
External Resources
WordPress Source Code
Other Resources