Как правильно работает __get() ?

class GET {

    public static $_vars, $_instance;

    /**
    * @return GET
    */
    public static function getInstance(){
        if(!isset(self::$_instance))
            self::$_instance = new GET();
        return self::$_instance;
    }

    public function __construct(){
        if(empty(self::$_vars))
            self::$_vars = $_GET;
        unset($this->pushState);
    }

    public function __get($name){
        return self::$_vars[$name];
    }

    public function __set($name, $value){
        self::$_vars[$name] = $value;
    }

    public function __isset($name){
        return isset(self::$_vars[$name]);
    }

    public function __unset($name){
        unset(self::$_vars[$name]);
    }
}

switch(GET::getInstance()->sort){
                case "recommend" :
                    $sort = "`c`.`position` ASC";
                    break;
                case "like" :
                    $sort = "`p`.`like` DESC";
                    break;
                case "high_price" :
                    $sort = "`p`.`price` DESC";
                    break;
                case "low_price" :
                    $sort = "`p`.`price` ASC";
                    break;
                default:
                    $sort = "`c`.`position` ASC";
                    break;
            }

public function __get($name){
      if(!isset(self::$_vars[$name]))
          return null;
      return self::$_vars[$name];
  }