public static function set_sort_field($sort_field) { switch ($sort_field) { case 'update': $sort_field = 'update_dt'; break; case 'create': $sort_field = 'create_dt'; break; case 'count': case 'id': break; default: $sort_field = 'sort_dt'; } Model_Kwalbum_Item::$_sort_field = $sort_field; }