/**
 *fetch value action
 */
 private static function fetchAction($fetchAction)
 {
     switch ($fetchAction) {
         case "assoc":
             self::$get_fetch_action = PDO::FETCH_ASSOC;
             //asso array
             break;
         case "num":
             self::$get_fetch_action = PDO::FETCH_NUM;
             //num array
             break;
         case "object":
             self::$get_fetch_action = PDO::FETCH_OBJ;
             //object array
             break;
         case "both":
             self::$get_fetch_action = PDO::FETCH_BOTH;
             //assoc array and num array
             break;
         default:
             self::$get_fetch_action = PDO::FETCH_ASSOC;
             break;
     }
     return self::$get_fetch_action;
 }