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1. jfache
   Member
   Posted 1 year ago #

   Hi there,

   I expect to filter my post meta prior to display and I thought that the new get_{$meta_type}_metadata filter could help but I don't get it.

   I'm basically trying to add a "TEST" string at the end of each post meta I want to display. Here's my code :

   function more_test($content) {
     return $content . "TEST";
   }
   
   add_filter('get_post_metadata', 'more_test');
   
   echo get_post_meta($post->ID, 'meta_test', true);

   It returns me "TEST" alone instead of the meta content + the "TEST" string. The meta content is stripped and if I try to echo it it's empty.

   What am I doing wrong? Is the get_post_metadata hook filter intended for another use?

   Thanks in advance for your help,
   Jeremy

2. David Carroll
   Member
   Posted 4 months ago #

   Hi jfache,

   Although it's been 10 months since you asked this question, you and others may still be interested.

   The issue with your code is the get_post_meta filter accepts 4 arguments, which needs to be reflected in your code. The following code example should work if your theme supports Featured Images.

   /* Description: Custom function to prevent post thumbnails from loading on search, category, and archive pages.
        * @param string|array $metadata - Always null for post metadata.
        * @param int $object_id - Post ID for post metadata
        * @param string $meta_key - metadata key.
        * @param bool $single - Indicates if processing only a single $metadata value or array of values.
        * @return Original or Modified $metadata.
        */
       function remove_post_thumbnail($metadata, $object_id, $meta_key, $single){
   
           //Return false if the current filter is that of a post thumbnail. Otherwise, return the original $content value.
           return ( isset($meta_key) && '_thumbnail_id' === $meta_key ) ? false : $metadata;
   
       }
   
       //Specify 4 arguments for this filter in the last parameter.
       add_filter('get_post_metadata', 'remove_post_thumbnail', true, 4);

   A good way to review how this works is reviewing the get_metadata() function in the /wp-includes/meta.php file.

   Look for the apply_filters line:

   $check = apply_filters( "get_{$meta_type}_metadata", null, $object_id, $meta_key, $single );

   Notice the second parameter is null. This is the first parameter ($metadata) in the custom filter function: remove_post_thumbnail().

   If the filter function returns anything other than null, the get_metadata() function will exit early. This is reflected in the conditional block immediately following the apply_filter() line.

   Hope this helps.

   David Carroll

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