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

User Contributed Notes

1. Skip to note 11 content

   Codex 9 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 47You must log in to vote on the helpfulness of this note

   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();

   • Don’t use this in themes you want to distribute. It won’t be possible to remove the action as $this would be a different value;

     theking2 2 years ago
2. Skip to note 12 content

   Codex 9 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 25You must log in to vote on the helpfulness of this note

   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();

   • If we have callback function which is static in another class, we can use the following: add_action( 'save_post', array( Classname::class, 'wpdocs_save_posts' ) );

     sumeetboga95 2 years ago
3. Skip to note 13 content

   Codex 9 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 10You must log in to vote on the helpfulness of this note

   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' );
4. Skip to note 14 content

   mkormendy 5 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 9You must log in to vote on the helpfulness of this note

   To pass a variable to the called function of the action, you can use closures (since PHP 5.3+) when the argument is not available in the original coded do_action. For example:

   add_action('wp_footer', function($arguments) use ($myvar) { 
       echo $myvar;
   }, $priority_integer, $accepted_arguments_integer);

   • Don’t use anonymous closures on themes you want to distribute. It would be impossible to remove the action. Instead use closure variables: $myvar = 'Hello World'; $action_wp_footer = function($arguments) use ($myvar) { echo $myvar; }; add_action('wp_footer', $action_wp_footer, 100, 1); which can be removed with: remove_action('wp_footer', $action_wp_footer, 100); with the advantage that typos in the closure name will yeild a helpfull Undfined variable error on typos.

     theking2 2 years ago
5. Skip to note 15 content

   Anthony Hortin 7 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 5You must log in to vote on the helpfulness of this note

   Related:

   do_action()
   remove_action()
6. Skip to note 16 content

   lucasbustamante 6 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 3You must log in to vote on the helpfulness of this note

   Passing parameters while using in a Class
   To pass parameters to your method in a Class while calling it with add_action, you can do as following:

   public function __construct() {
       // Actions
       add_action('init', array($this, 'call_somefunction'));
   }
   
   /**
    *    Intermediate function to call add_action with parameters
    */
   public function call_somefunction() {
       $this->somefunction('Hello World');
   }
   
   /**
    *    Actual function that does something
    */
   public function somefunction($text) {
       echo $text;
   }
7. Skip to note 17 content

   Bartek 1 year ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 3You must log in to vote on the helpfulness of this note

   I urge you, don’t attach your hook callbacks inside class’ constructor.

   Instead of implementing official example most upvoted in this thread, opt for decoupled solution. You have one more line of code to write, but objects become more reusable and less error-prone (consider, what would happen if you call new WP_Docs_Class() twice in your code, following Codex example).

   /**
    * Class WP_Docs_Class.
    */
   class WP_Docs_Class {
   	
   	/**
   	 * Initiate all hooks' callbacks in a separate method.
   	 */
   	public function hooks() {
   		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();
   $wpdocsclass->hooks();
8. Skip to note 18 content

   Christian Saborio 4 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 2You must log in to vote on the helpfulness of this note

   How to add an action that calls a function (with parameters) from an instantiated class:

   $admin_menu_hider = new AdminMenuHider( UserManagement::get_internal_users() );
   			add_action(
   				'wp_before_admin_bar_render',
   				function () use ( $admin_menu_hider ) {
   					$admin_menu_hider->change_greeting_message( 'Hello' );
   				}
   			);
9. Skip to note 19 content

   Codex 9 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 1You must log in to vote on the helpfulness of this note

   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 );
10. Skip to note 20 content

    theking2 2 years ago

    You must log in to vote on the helpfulness of this noteVote results for this note: -4You must log in to vote on the helpfulness of this note

    To prevent runtime errors due to easy typo errors (defensive programming) and prevent pollution of the global namespace use closures instead of function names. The sample code adjusted:

    /**
     * add a save post hook
     */
    add_action( 'save_post', function( $post_ID, $post, $update ) {
       // do stuff here
    }, 10, 3 );

    • Do not do this in themes or plugins you intend to distribute, as it will prevent others from removing your callables if desired.

      crstauf 2 years ago
    • Not recommended, as you would be missing a valuable callback function name in any stack trace.

      Dave Green 2 years ago