[wp-trac] [WordPress Trac] #38743: Introduce add_action_once()

[WordPress Trac]

#38743: Introduce add_action_once()
-----------------------------+------------------------------
 Reporter:  tfrommen         |       Owner:
     Type:  feature request  |      Status:  new
 Priority:  normal           |   Milestone:  Awaiting Review
Component:  General          |     Version:
 Severity:  normal           |  Resolution:
 Keywords:                   |     Focuses:
-----------------------------+------------------------------

Comment (by tfrommen):

 Seems like I'm unable to edit this ticket...

 The second function should look like this, acutally:

 {{{#!php
 <?php

 function add_filter_once(
     $tag,
     callable $function_to_add,
     $priority = 10,
     $accepted_args = 1,
     $check_priority = false
 ) {

     global $wp_filter;

     if ( empty( $wp_filter[ $tag ] ) ) {
         return add_filter( $tag, $function_to_add, $priority,
 $accepted_args );
     }

     if ( false === $check_priority ) ) {
         if ( has_filter( $tag, $function_to_add ) ) {
             return false;
         }
     } else {
         if ( empty( $wp_filter[ $tag ][ $check_priority ] ) {
             return add_filter( $tag, $function_to_add, $priority,
 $accepted_args );
         }

         foreach ( $wp_filter[ $tag ][ $check_priority ] as $data ) {
             if ( isset( $data['function'] ) && $function_to_add ===
 $data['function'] ) {
                 return false;
             }
         }
     }

     return add_filter( $tag, $function_to_add, $priority, $accepted_args
 );
 }
 }}}

 I had several version here, with and without `has_filter()` - and mixed
 them up. :)

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Ticket URL: <https://core.trac.wordpress.org/ticket/38743#comment:1>
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