public function getPaymentOptions($payKey, $details = false)
    {
        $operation = ($details) ? 'PaymentDetails' : 'GetPaymentOptions';

        $this->setRequestData([
            'requestEnvelope' => $this->setEnvelope(),
            'payKey'          => $payKey,
        ]);

        return $this->doPayPalRequest($operation);
    }