Title: Functions | Developer.WordPress.org --- # Functions * function[absint()](https://developer.wordpress.org/reference/functions/absint/) * Converts a value to non-negative integer. * Used by [129 functions](https://developer.wordpress.org/reference/functions/absint/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/absint/#uses) | Source: [wp-includes/load.php:1468](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/load.php#L1468-L1470) * function[activate_plugin()](https://developer.wordpress.org/reference/functions/activate_plugin/) * Attempts activation of plugin in a “sandbox” and redirects on success. * Used by [3 functions](https://developer.wordpress.org/reference/functions/activate_plugin/#used-by) | Uses [17 functions](https://developer.wordpress.org/reference/functions/activate_plugin/#uses) | Source: [wp-admin/includes/plugin.php:641](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L641-L742) * function[activate_plugins()](https://developer.wordpress.org/reference/functions/activate_plugins/) * Activates multiple plugins. * Used by [0 functions](https://developer.wordpress.org/reference/functions/activate_plugins/#used-by) | Uses [5 functions](https://developer.wordpress.org/reference/functions/activate_plugins/#uses) | Source: [wp-admin/includes/plugin.php:869](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L869-L890) * function[activate_sitewide_plugin()](https://developer.wordpress.org/reference/functions/activate_sitewide_plugin/) * Deprecated functionality for activating a network-only plugin. * Used by [0 functions](https://developer.wordpress.org/reference/functions/activate_sitewide_plugin/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/activate_sitewide_plugin/#uses) | Source: [wp-admin/includes/ms-deprecated.php:57](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/ms-deprecated.php#L57-L60) * function[addslashes_gpc()](https://developer.wordpress.org/reference/functions/addslashes_gpc/) * Adds slashes to a string or recursively adds slashes to strings within an array. * Used by [0 functions](https://developer.wordpress.org/reference/functions/addslashes_gpc/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/addslashes_gpc/#uses) | Source: [wp-includes/deprecated.php:6503](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/deprecated.php#L6503-L6506) * function[addslashes_strings_only()](https://developer.wordpress.org/reference/functions/addslashes_strings_only/) * Adds slashes only if the provided value is a string. * Used by [0 functions](https://developer.wordpress.org/reference/functions/addslashes_strings_only/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/addslashes_strings_only/#uses) | Source: [wp-includes/deprecated.php:4141](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/deprecated.php#L4141-L4143) * function[add_action()](https://developer.wordpress.org/reference/functions/add_action/) * Adds a callback function to an action hook. * Used by [90 functions](https://developer.wordpress.org/reference/functions/add_action/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_action/#uses) | Source: [wp-includes/plugin.php:446](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/plugin.php#L446-L448) * function[add_allowed_options()](https://developer.wordpress.org/reference/functions/add_allowed_options/) * Adds an array of options to the list of allowed options. * Used by [2 functions](https://developer.wordpress.org/reference/functions/add_allowed_options/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/add_allowed_options/#uses) | Source: [wp-admin/includes/plugin.php:2283](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L2283-L2305) * function[add_blog_option()](https://developer.wordpress.org/reference/functions/add_blog_option/) * Adds a new option for a given blog ID. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_blog_option/#used-by) | Uses [4 functions](https://developer.wordpress.org/reference/functions/add_blog_option/#uses) | Source: [wp-includes/ms-blogs.php:404](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/ms-blogs.php#L404-L420) * function[add_clean_index()](https://developer.wordpress.org/reference/functions/add_clean_index/) * Adds an index to a specified table. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_clean_index/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/add_clean_index/#uses) | Source: [wp-admin/includes/upgrade.php:2743](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/upgrade.php#L2743-L2750) * function[add_comments_page()](https://developer.wordpress.org/reference/functions/add_comments_page/) * Adds a submenu page to the Comments main menu. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_comments_page/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_comments_page/#uses) | Source: [wp-admin/includes/plugin.php:1844](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L1844-L1846) * function[add_comment_meta()](https://developer.wordpress.org/reference/functions/add_comment_meta/) * Adds meta data field to a comment. * Used by [3 functions](https://developer.wordpress.org/reference/functions/add_comment_meta/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_comment_meta/#uses) | Source: [wp-includes/comment.php:471](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/comment.php#L471-L473) * function[add_contextual_help()](https://developer.wordpress.org/reference/functions/add_contextual_help/) * Add contextual help text for a page. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_contextual_help/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/add_contextual_help/#uses) | Source: [wp-admin/includes/deprecated.php:997](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/deprecated.php#L997-L1004) * function[add_cssclass()](https://developer.wordpress.org/reference/functions/add_cssclass/) * Adds a CSS class to a string. * Used by [1 function](https://developer.wordpress.org/reference/functions/add_cssclass/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/add_cssclass/#uses) | Source: [wp-admin/includes/menu.php:212](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/menu.php#L212-L218) * function[add_custom_background()](https://developer.wordpress.org/reference/functions/add_custom_background/) * Add callbacks for background image display. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_custom_background/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/add_custom_background/#uses) | Source: [wp-includes/deprecated.php:3046](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/deprecated.php#L3046-L3056) * function[add_custom_image_header()](https://developer.wordpress.org/reference/functions/add_custom_image_header/) * Add callbacks for image header display. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_custom_image_header/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/add_custom_image_header/#uses) | Source: [wp-includes/deprecated.php:3010](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/deprecated.php#L3010-L3019) * function[add_dashboard_page()](https://developer.wordpress.org/reference/functions/add_dashboard_page/) * Adds a submenu page to the Dashboard main menu. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_dashboard_page/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_dashboard_page/#uses) | Source: [wp-admin/includes/plugin.php:1724](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L1724-L1726) * function[add_editor_style()](https://developer.wordpress.org/reference/functions/add_editor_style/) * Adds callback for custom TinyMCE editor stylesheets. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_editor_style/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/add_editor_style/#uses) | Source: [wp-includes/theme.php:2184](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/theme.php#L2184-L2198) * function[add_existing_user_to_blog()](https://developer.wordpress.org/reference/functions/add_existing_user_to_blog/) * Adds a user to a blog based on details from maybe_add_existing_user_to_blog(). * Used by [1 function](https://developer.wordpress.org/reference/functions/add_existing_user_to_blog/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/add_existing_user_to_blog/#uses) | Source: [wp-includes/ms-functions.php:2275](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/ms-functions.php#L2275-L2293) * function[add_feed()](https://developer.wordpress.org/reference/functions/add_feed/) * Adds a new feed type like /atom1/. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_feed/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/add_feed/#uses) | Source: [wp-includes/rewrite.php:251](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/rewrite.php#L251-L266) * function[add_filter()](https://developer.wordpress.org/reference/functions/add_filter/) * Adds a callback function to a filter hook. * Used by [120 functions](https://developer.wordpress.org/reference/functions/add_filter/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/add_filter/#uses) | Source: [wp-includes/plugin.php:121](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/plugin.php#L121-L131) * function[add_image_size()](https://developer.wordpress.org/reference/functions/add_image_size/) * Registers a new image size. * Used by [2 functions](https://developer.wordpress.org/reference/functions/add_image_size/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_image_size/#uses) | Source: [wp-includes/media.php:300](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/media.php#L300-L308) * function[add_link()](https://developer.wordpress.org/reference/functions/add_link/) * Adds a link using values provided in $_POST. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_link/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_link/#uses) | Source: [wp-admin/includes/bookmark.php:16](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/bookmark.php#L16-L18) * function[add_links_page()](https://developer.wordpress.org/reference/functions/add_links_page/) * Adds a submenu page to the Links main menu. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_links_page/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_links_page/#uses) | Source: [wp-admin/includes/plugin.php:1796](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L1796-L1798) * function[add_magic_quotes()](https://developer.wordpress.org/reference/functions/add_magic_quotes/) * Walks the array while sanitizing the contents. * Used by [4 functions](https://developer.wordpress.org/reference/functions/add_magic_quotes/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_magic_quotes/#uses) | Source: [wp-includes/functions.php:1288](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/functions.php#L1288-L1298) * function[add_management_page()](https://developer.wordpress.org/reference/functions/add_management_page/) * Adds a submenu page to the Tools main menu. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_management_page/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_management_page/#uses) | Source: [wp-admin/includes/plugin.php:1599](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L1599-L1601) * function[add_media_page()](https://developer.wordpress.org/reference/functions/add_media_page/) * Adds a submenu page to the Media main menu. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_media_page/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/add_media_page/#uses) | Source: [wp-admin/includes/plugin.php:1772](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L1772-L1774) * function[add_menu_classes()](https://developer.wordpress.org/reference/functions/add_menu_classes/) * Adds CSS classes for top-level administration menu items. * Used by [0 functions](https://developer.wordpress.org/reference/functions/add_menu_classes/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/add_menu_classes/#uses) | Source: [wp-admin/includes/menu.php:230](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/menu.php#L230-L278) * function[add_menu_page()](https://developer.wordpress.org/reference/functions/add_menu_page/) * Adds a top-level menu page. * Used by [2 functions](https://developer.wordpress.org/reference/functions/add_menu_page/#used-by) | Uses [8 functions](https://developer.wordpress.org/reference/functions/add_menu_page/#uses) | Source: [wp-admin/includes/plugin.php:1391](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/plugin.php#L1391-L1452) * function[add_meta()](https://developer.wordpress.org/reference/functions/add_meta/) * Adds post meta data defined in the `$_POST` superglobal for a post with given ID. * Used by [3 functions](https://developer.wordpress.org/reference/functions/add_meta/#used-by) | Uses [5 functions](https://developer.wordpress.org/reference/functions/add_meta/#uses) | Source: [wp-admin/includes/post.php:1008](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-admin/includes/post.php#L1008-L1041) 1 [2](https://developer.wordpress.org/reference/functions/page/2/?output_format=md) [3](https://developer.wordpress.org/reference/functions/page/3/?output_format=md)… [49](https://developer.wordpress.org/reference/functions/page/49/?output_format=md) [Next Page](https://developer.wordpress.org/reference/functions/page/2/?output_format=md)