add_action( string $hook_name, callable $callback, int $priority = 10, int $accepted_args = 1 )

Adds a callback function to an action hook.

Description

Actions are the hooks that the WordPress core launches at specific points during execution, or when specific events occur. Plugins can specify that one or more of its PHP functions are executed at these points, using the Action API.

Parameters

$hook_name

(Required) The name of the action to add the callback to.

$callback

(Required) The callback to be run when the action is called.

$priority

(Optional) Used to specify the order in which the functions associated with a particular action are executed.<br> Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.

Default value: 10

$accepted_args

(Optional) The number of arguments the function accepts.

Default value: 1

Return

(true) Always returns true.

Source

File: wp-includes/plugin.php 

function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
	return add_filter($tag, $function_to_add, $priority, $accepted_args);
}

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Related

Uses

Uses
Uses Description
wp-includes/plugin.php: add_filter()

Adds a callback function to a filter hook.

Used By

Used By
Used By Description
wp-admin/includes/meta-boxes.php: register_and_do_post_meta_boxes()

Registers the default post meta boxes, and runs the do_meta_boxes actions.
wp-includes/classicpress/class-wp-compat.php: WP_Compat::__construct()
wp-includes/classicpress/class-cp-customization-frontend.php: CP_Customization_Frontend::__construct()
wp-includes/classicpress/class-cp-customization.php: CP_Customization::__construct()
wp-includes/classicpress/class-cp-customization.php: CP_Customization::add_id_init()

Add ID column to Post / Page Tables
wp-includes/ms-site.php: wp_is_site_initialized()

Checks whether a site is initialized.
wp-login.php: login_header()

Output the login page header.
wp-includes/customize/class-wp-customize-site-icon-control.php: WP_Customize_Site_Icon_Control::__construct()

Constructor.
wp-includes/customize/class-wp-customize-nav-menu-item-setting.php: WP_Customize_Nav_Menu_Item_Setting::__construct()

Constructor.
wp-includes/customize/class-wp-customize-header-image-control.php: WP_Customize_Header_Image_Control::prepare_control()
wp-includes/general-template.php: add_thickbox()

Enqueues the default ThickBox js and css.
wp-includes/widgets/class-wp-widget-text.php: WP_Widget_Text::_register_one()

Add hooks for enqueueing assets when registering all widget instances of this widget class.
wp-includes/widgets/class-wp-widget-recent-comments.php: WP_Widget_Recent_Comments::__construct()

Sets up a new Recent Comments widget instance.
wp-includes/widgets/class-wp-widget-custom-html.php: WP_Widget_Custom_HTML::_register_one()

Add hooks for enqueueing assets when registering all widget instances of this widget class.
wp-includes/widgets/class-wp-widget-media.php: WP_Widget_Media::_register_one()

Add hooks while registering all widget instances of this widget class.
wp-includes/media-template.php: wp_print_media_templates()

Prints the templates used in the media manager.
wp-includes/nav-menu.php: _wp_delete_customize_changeset_dependent_auto_drafts()

Deletes auto-draft posts associated with the supplied changeset.
wp-includes/cron.php: wp_cron()

Registers _wp_cron() to run on the {@see ‘wp_loaded’} action.
wp-includes/theme.php: _custom_header_background_just_in_time()

Registers the internal custom header and background routines.
wp-includes/plugin.php: register_activation_hook()

Set the activation hook for a plugin.
wp-includes/plugin.php: register_deactivation_hook()

Sets the deactivation hook for a plugin.
wp-includes/rewrite.php: add_feed()

Adds a new feed type like /atom1/.
wp-admin/includes/class-theme-upgrader.php: Theme_Upgrader::install()

Install a theme package.
wp-admin/includes/class-theme-upgrader.php: Theme_Upgrader::upgrade()

Upgrade a theme.
wp-admin/includes/plugin.php: add_menu_page()

Adds a top-level menu page.
wp-admin/includes/plugin.php: add_submenu_page()

Adds a submenu page.
wp-admin/includes/plugin.php: uninstall_plugin()

Uninstalls a single plugin.
wp-admin/includes/class-language-pack-upgrader.php: Language_Pack_Upgrader::bulk_upgrade()

Bulk upgrade language packs.
wp-admin/includes/class-wp-theme-install-list-table.php: WP_Theme_Install_List_Table::prepare_items()
wp-admin/includes/update.php: wp_plugin_update_rows()

Adds a callback to display update information for plugins with updates available.
wp-admin/includes/update.php: wp_theme_update_rows()

Adds a callback to display update information for themes with updates available.
wp-admin/includes/class-plugin-upgrader.php: Plugin_Upgrader::upgrade()

Upgrade a plugin.
wp-admin/includes/class-plugin-upgrader.php: Plugin_Upgrader::install()

Install a plugin package.
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Changelog

Changelog
Version Description
1.2.0 Introduced.