[wp-trac] [WordPress Trac] #19986: Issue with add_filter() and add_action() when using anonymous functions.

[WordPress Trac]

#19986: Issue with add_filter() and add_action() when using anonymous functions.
--------------------------+-----------------------------
 Reporter:  pagesimplify  |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Plugins       |    Version:  3.3.1
 Severity:  normal        |   Keywords:  has-patch
--------------------------+-----------------------------
 Referencing File: /wp-includes/plugin.php :: function add_filter()
 {{{
 function add_filter($tag, $function_to_add, $priority = 10, $accepted_args
 = 1) {
         global $wp_filter, $merged_filters;

         $idx = _wp_filter_build_unique_id($tag, $function_to_add,
 $priority);
         $wp_filter[$tag][$priority][$idx] = array('function' =>
 $function_to_add, 'accepted_args' => $accepted_args);
         unset( $merged_filters[ $tag ] );
         return true;
 }
 }}}

 When registering a function with add_filter() and add_action(), a unique
 id ($idx) is generated to be used as an array key in:

 {{{
 $wp_filter[$tag][$priority][$idx]
 }}}

 The function that creates this unique key ($idx) returns the function name
 passed into the $function_to_add parameter.
 {{{
 $idx = _wp_filter_build_unique_id($tag, $function_to_add, $priority);
 }}}

 If the $function_to_add parameter is a string, the function
 _wp_filter_build_unique_id() returns the original function name.

 {{{
 function _wp_filter_build_unique_id($tag, $function, $priority) {
         global $wp_filter;
         static $filter_id_count = 0;

         if ( is_string($function) )
                 return $function;
    ...
 }
 }}}

 Returning a string value for the unique id is a problem when the function
 is an anonymous function generated using create_function(). The reason is
 anonymous functions are named as "special character + lambda_XX" or as
 "ºlambda_XX" where the first character cannot be displayed.

 See attached file: anonymous_function_name.jpg

 Since array keys can only be integers or strings, the following array is
 invalid and causes inconsistent behaviors.

 {{{
 $wp_filter[$tag][$priority]['ºlambda_XX']
 }}}

 Although I've seen instances where this will still work, I've also
 observed strange issues with inconsistent results where plugins should
 work and sometimes do not. One example is with Otto's Simple Facebook
 Connect plugin.

 See file: sfc-widgets.php
 {{{
 add_action('widgets_init', create_function('', 'return
 register_widget("SFC_Fan_Box_Widget");'));
 }}}

 I have not been able to isolate the conditions that allow this to work in
 one WordPress installation and not in others. However, I have been able to
 apply a patch to my installation with consistent and successful results.

 See attached patch: plugin.php.diff

 While this is an obscure and possibly very isolated issue, it could
 resolve unexplained issues related to using anonymous functions with
 add_filter() elsewhere.

-- 
Ticket URL: <http://core.trac.wordpress.org/ticket/19986>
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