Using WordPress ‘delete_{$meta_type}_meta’ PHP action

by

The delete_{$meta_type}_meta WordPress PHP action fires immediately before deleting metadata of a specific type.

Usage

add_action('delete_post_meta', 'your_custom_function', 10, 4);

function your_custom_function($meta_ids, $object_id, $meta_key, $_meta_value) {
    // your custom code here

    return $meta_ids;
}

Parameters

  • $meta_ids (string[]): An array of metadata entry IDs to delete.
  • $object_id (int): ID of the object metadata is for.
  • $meta_key (string): Metadata key.
  • $_meta_value (mixed): Metadata value.

More information

See WordPress Developer Resources: delete_{$meta_type}_meta

Examples

Log metadata deletion for posts

Log each time a post’s metadata is deleted.

add_action('delete_post_meta', 'log_post_meta_deletion', 10, 4);

function log_post_meta_deletion($meta_ids, $object_id, $meta_key, $_meta_value) {
    error_log("Post meta deleted: object_id - {$object_id}, meta_key - {$meta_key}");
    return $meta_ids;
}

Prevent deletion of specific metadata for users

Prevent deletion of the ‘custom_field’ metadata for users.

add_action('delete_user_meta', 'prevent_custom_field_deletion', 10, 4);

function prevent_custom_field_deletion($meta_ids, $object_id, $meta_key, $_meta_value) {
    if ($meta_key === 'custom_field') {
        return false;
    }

    return $meta_ids;
}

When a term’s ‘main_image’ metadata is deleted, also delete the ‘thumbnail_image’ metadata.

add_action('delete_term_meta', 'delete_related_term_meta', 10, 4);

function delete_related_term_meta($meta_ids, $object_id, $meta_key, $_meta_value) {
    if ($meta_key === 'main_image') {
        delete_term_meta($object_id, 'thumbnail_image');
    }

    return $meta_ids;
}

Notify admin when comment metadata is deleted

Send a notification to the admin when a comment’s ‘custom_flag’ metadata is deleted.

add_action('delete_comment_meta', 'notify_admin_on_custom_flag_removal', 10, 4);

function notify_admin_on_custom_flag_removal($meta_ids, $object_id, $meta_key, $_meta_value) {
    if ($meta_key === 'custom_flag') {
        $admin_email = get_option('admin_email');
        wp_mail($admin_email, 'Custom Flag Removed', 'The custom flag has been removed from comment ID: ' . $object_id);
    }

    return $meta_ids;
}

Clear cache when post metadata is deleted

Clear the cache for a post when its metadata is deleted.

add_action('delete_post_meta', 'clear_post_cache_on_meta_deletion', 10, 4);

function clear_post_cache_on_meta_deletion($meta_ids, $object_id, $meta_key, $_meta_value) {
    wp_cache_delete($object_id, 'posts');
    return $meta_ids;
}