add_action ( string $tag, callable $function_to_add, int $priority = 10, int $accepted_args = 1 )

Hooks a function on to a specific action.

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.

Return: (true) Will always return true.

Source file: wp-includes/plugin.php

View source


Parameters

$tag

(string) (Required) The name of the action to which the $function_to_add is hooked.

$function_to_add

(callable) (Required) The name of the function you wish to be called.

$priority

(int) (Optional) Used to specify the order in which the functions associated with a particular action are executed. 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

(int) (Optional) The number of arguments the function accepts.

Default value: 1


More Information

Usage

add_action( $hook, $function_to_add, $priority, $accepted_args );

To find out the number and name of arguments for an action, simply search the code base for the matching do_action() call. For example, if you are hooking into ‘save_post’, you would find it in post.php:

do_action( 'save_post', $post_ID, $post, $update );

Your add_action call would look like:

add_action( 'save_post', 'wpdocs_my_save_post', 10, 3 );

And your function would be:

function wpdocs_my_save_post( $post_ID, $post, $update ) {
   // do stuff here
}

Used by


Source

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


Changelog


User Contributed Notes

  1. Simple Hook
    To email some friends whenever an entry is posted on your blog:

    /**
     * Send email to my friends.
     *
     * @param int $post_id Post ID.
     * @return int Post ID.
     */
    function wpdocs_email_friends( $post_id ) {
    	$friends = 'bob@example.org, susie@example.org';
    	wp_mail( $friends, "sally's blog updated", 'I just put something on my blog: http://blog.example.com' );
    
    	return $post_id;
    }
    add_action( 'publish_post', 'wpdocs_email_friends' );
    
  2. Accepted Arguments
    A hooked function can optionally accept arguments from the action call, if any are set to be passed. In this simplistic example, the echo_comment_id function takes the $comment_id argument, which is automatically passed to when the do_action() call using the comment_id_not_found filter hook is run.

    /**
     * Warn about comment not found
     *
     * @param int $comment_id Comment ID.
     */
    function echo_comment_id( $comment_id ) {
    	printf( 'Comment ID %s could not be found', esc_html( $comment_id ) );
    }
    add_action( 'comment_id_not_found', 'echo_comment_id', 10, 1 );
    
  3. Using with a Class
    To use add_action() when your plugin or theme is built using classes, you need to use the array callable syntax. You would pass the function to add_action() as an array, with $this as the first element, then the name of the class method, like so:

    /**
     * Class WP_Docs_Class.
     */
    class WP_Docs_Class {
    
    	/**
    	 * Constructor
    	 */
    	public function __construct() {
    		add_action( 'save_post', array( $this, 'wpdocs_save_posts' ) );
    	}
    
    	/**
    	 * Handle saving post data.
    	 */
    	public function wpdocs_save_posts() {
    		// do stuff here...
    	}
    }
    
    $wpdocsclass = new WP_Docs_Class();
    
  4. Using with static functions in a class
    If the class is called staticly the approach has to be like below as $this is not available. This also works if class is extended. Use the following:

    /**
     * Class WP_Docs_Static_Class.
     */
    class WP_Docs_Static_Class {
    
    	/**
    	 * Initializer for setting up action handler
    	 */
    	public static function init() {
    		add_action( 'save_post', array( get_called_class(), 'wpdocs_save_posts' ) );
    	}
    
    	/**
    	 * Handler for saving post data.
    	 */
    	public static function wpdocs_save_posts() {
    		// do stuff here...
    	}
    }
    
    WP_Docs_Static_Class::init();
    

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