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Function Reference

The files of WordPress define many useful PHP functions. Some of the functions, known as Template Tags, are defined especially for use in WordPress Themes. There are also some functions related to actions and filters (the Plugin API), which are therefore used primarily for developing Plugins. The rest are used to create the core WordPress functionality.

Many of the core WordPress functions are useful to Plugin and Theme developers. So, this article lists most of the core functions, excluding Template Tags. At the bottom of the page, there is a section listing other resources for finding information about WordPress functions. In addition to this information, the WordPress phpdoc site details all the WordPress functions by version since 2.6.1.

You can help make this page more complete!

Here are some things you can do to help:

  • Add documentation to un-documented functions, by creating sub-pages or at least by adding short comments in the lists below. If you create a subpage for a function, please include information and examples of usage of that function, if possible, per the examples found in Template Tags.
  • List more functions here, following the category structure.
  • Correct errors by moving functions to better categories where appropriate, and of course fixing typos. Note: that it is OK for a function to appear in more than one category.

Read Contributing to WordPress to find out more about how you can contribute to the effort!

Functions by category

Post, Custom Post Type, Page, Attachment and Bookmarks Functions

Posts

Custom Post Type

Post insertion/removal

Pages

Custom Fields (postmeta)

Attachments

Bookmarks

Terms


Others

Category, Tag and Taxonomy Functions

Categories

Category Creation

Tags

Taxonomy

User and Author Functions

Admins, Roles and Capabilities

Users and Authors

User meta

User insertion/removal

Login / Logout

Feed Functions

HTTP API Functions


Comment, Ping, and Trackback Functions

Comments Loop

Comments Pagination


Action, Filter, and Plugin Functions

Filters (Reference)

Actions (Reference)

Plugins (Reference)

Widgets (Reference)


Settings (Reference)

Shortcodes (Reference)

Theme-Related Functions

Include functions

Other functions

Formatting Functions

Miscellaneous Functions

Time/Date Functions

Serialization

Options

Transients

Admin Menu Functions

Toolbar Functions

Form Helpers


Nonces and Referers (Security)

XMLRPC

Localization

Cron (Scheduling)

Conditional Tags Index

Script and Style Registration

sql

Miscellaneous

Multisite functions

As of v3.0, WordPress includes WPMU functionality. Old WPMU functions reference can be found at http://codex.wordpress.org/WPMU_Functions (deprecated page).

Multisite administration Functions

These functions are found in file wp-admin/includes/ms.php (since 3.0.0).


Multisite Functions

Site/blog functions that work with the blogs table and related data, found in file wp-includes/ms-blogs.php (since 3.0.0).

Defines constants and global variables that can be overridden, generally in wp-config.php, found in file wp-includes/ms-default-constants.php (since 3.0.0).

Multisite WordPress API, found in file wp-includes/ms-functions.php (since 3.0.0).

These functions are needed to load Multisite, found in file wp-includes/ms-load.php (since 3.0.0).

Official and Unofficial References

  • WordPress.org PHPDoc - Nearly all the functions in WordPress have "PHPDoc" headers. This site shows all the PHPDoc.
  • Trac Browser - WordPress source code. Choose 'Tags' to find a specific version source code, or 'Trunk' to see the latest version source code.
  • PHPXref for WordPress - Cross reference of WordPress files, functions, and variables, which seems to point to the latest released version.
  • WordPress Function History Table - List each WordPress function with including the version it was introduced in or dropped in. PlanetOzh recommends: "see related WordPress Functions Implementation History Tool for more information (and for a more usable tool)"
  • WordPress Variable Report - A list of WordPress functions, listing what version of PHP every function requires (and if there's a compatible function available), what varables/arguments in functions are unused, and what functions/variables each class contains (and their default values).
  • WordPress Hooks Table - A list of WordPress actions and filters, cross-referenced to the files they are in