Anonymous functions in WordPress hooks

Question

WordPress hooks can be used in two ways:

1. using callback function name and appropriate function

   add_action( 'action_name', 'callback_function_name' );
   function callback_function_name() {
       // do something
   }
   

2. using anonymous function (closure)

   add_action( 'action_name', function() {
       // do something
   } );
   

Is there any difference for WordPress what way to use? What is prefered way and why?

Answer 1

The disadvantage of the anonymous function is that you're not able to remove the action with remove_action.

Important: To remove a hook, the $function_to_remove and $priority arguments must match when the hook was added. This goes for both filters and actions. No warning will be given on removal failure.

Because you didn't define function_to_remove, you can't remove it.

So you should never use this inside plugins or themes that somebody else might want to overwrite.