/**
  * @since 2.0.8
  */
 private static function add_where_to_query($add_where, &$where_clause)
 {
     if (is_array($where_clause)) {
         $where_clause[] = $add_where;
     } else {
         global $wpdb;
         $where = '';
         $values = array();
         FrmDb::parse_where_from_array($add_where, '', $where, $values);
         FrmDb::get_where_clause_and_values($add_where);
         $where_clause .= ' AND (' . $wpdb->prepare($where, $values) . ')';
     }
 }