Money\Money::__construct PHP Метод

    private function __construct($amount, Currency $currency)
    {
        $this->amount = $amount;
        $this->currency = $currency;
    }

 /**
  * @param integer $amount
  */
 public function __construct($amount, Currency $currency = null)
 {
     if ($currency === null) {
         $currency = new Currency(self::DEFAULT_CURRENCY_NAME);
     }
     parent::__construct($amount, $currency);
 }