public function __construct($merchantId = null, $secretKey = null, $paymentEndpointUrl = null, $loyaltyInquiryEndPointUrl = null, $paymentReturnPointUrl = null)
{
$this->merchantId = $merchantId;
$this->secretKey = $secretKey;
$this->paymentEndpointUrl = $paymentEndpointUrl;
$this->loyaltyInquiryEndPointUrl = $loyaltyInquiryEndPointUrl;
$this->paymentReturnPointUrl = $paymentReturnPointUrl;
}