我试图将Paypal作为支付网关集成到我的Laravel 5.8网站中。为了做到这一点，我使用了Laravel-Omnipay包，它提供了Omnipay集成到Laravel中。
至于我的Paypal商业账户，我已经设置了我的凭据。使用paypal沙箱和以下代码工作：

Route::get('paypal', function() {
    $gateway = Omnipay::create('PayPal_Rest');

    $gateway->initialize(array(
        'clientId' => 'MySandboxClientId',
        'secret'   => 'MySandboxSecret',
        'testMode' => true,
    ));
    $card = new CreditCard(array(
        'firstName' => 'first name',
        'lastName' => 'last name',
        'number' => '5498876202508868',
        'cvv' => '123',
        'expiryMonth'           => '09',
        'expiryYear'            => '2024',
        'billingAddress1'       => '1 Scrubby Creek Road',
        'billingCountry'        => 'AU',
        'billingCity'           => 'Scrubby Creek',
        'billingPostcode'       => '4999',
        'billingState'          => 'QLD',
    ));
    try {
        $transaction = $gateway->purchase(array(
            'amount'        => '10.00',
            'currency'      => 'USD',
            'description'   => 'This is a test purchase transaction.',
            'card'          => $card,
        ));
        $response = $transaction->send();
        $data = $response->getData();
        dd($data);
        echo "Gateway purchase response data == " . print_r($data, true) . "\n";

        if ($response->isSuccessful()) {
            echo "Purchase transaction was successful!\n";
        }
    } catch (\Exception $e) {
        echo "Exception caught while attempting authorize.\n";
        echo "Exception type == " . get_class($e) . "\n";
        echo "Message == " . $e->getMessage() . "\n";
    }
});

但是，当我尝试使用自己的信用卡进行实时支付时，我会出现Unauthorized payment.错误。我使用的代码与上面的代码相同，我只是将clientId和secret替换为我的实时沙盒凭据。
我怎样才能实时调用REST API？我需要进行1美元的交易，以便测试该卡是否有效。