wp_delete_object_term_relationships triggers PHP warning when object has no terms in taxonomy

[ragulka]

If using wp_delete_object_term_relationships on an onbject with a taxonomy, where the object does not have any terms in that taxonomy, the function triggers a PHP Warning, sicne it's trying to map an array, where there is none.

The function body is like this:

  $object_id = (int) $object_id;

  if ( !is_array($taxonomies) )
    $taxonomies = array($taxonomies);

  foreach ( (array) $taxonomies as $taxonomy ) {
    $term_ids = wp_get_object_terms( $object_id, $taxonomy, array( 'fields' => 'ids' ) ); 
    $term_ids = array_map( 'intval', $term_ids );
    wp_remove_object_terms( $object_id, $term_ids, $taxonomy );
  }

But should probably be like this:

  $object_id = (int) $object_id;

  if ( !is_array($taxonomies) )
    $taxonomies = array($taxonomies);

  foreach ( (array) $taxonomies as $taxonomy ) {
    $term_ids = wp_get_object_terms( $object_id, $taxonomy, array( 'fields' => 'ids' ) );
    if ( empty( $term_ids ) {
      continue;
    }  
    $term_ids = array_map( 'intval', $term_ids );
    wp_remove_object_terms( $object_id, $term_ids, $taxonomy );
  }

[boonebgorges]

Confirmed. Thanks for the report.

[boonebgorges]

In 31021:

Add tests for wp_delete_object_term_relationships().

See #30879.

[boonebgorges]

Actually, I take back the "confirmed". It turns out I could reproduce a PHP notice only if I used an invalid taxonomy (in which case wp_get_object_terms() returns a WP_Error object). In all other cases, wp_get_object_terms() returns an array, even if it's an empty array.

ragulka, could you please double check what's happening here? Exactly what value is being passed to array_map()? If it turns out that it's a WP_Error object, we're going to have to get creative here, since the error provides a valuable notice to developers, but wp_delete_object_term_relationships() doesn't have a return value.

[ragulka]

boonebgorges, I think you're right. I don't have the environment where I encountered this available, but I think I might have called the function before init, which means that my custom taxonomy wasn't registered yet.

[boonebgorges]

@ragulka - Thanks for reporting back. On that assumption, I'm going to close this ticket. This is the kind of PHP notice that actually does a service to the developer, by letting them know that something is wrong with their code instead of failing silently.