Paypal PHP Integration Omnipay中的“无效请求-查看详细信息”

Question

我已经将此Paypal Payment与Omnipay集成到了我的php应用程序中

在我的index.php中，

<form action="process.php" method="POST">
    <button type="submit">Pay with Paypal</button>
</form>

在我的process.php中，我已经完成了

<?php

require_once 'config.php';
 
try {
    $response = $gateway->purchase(array(
        'amount' => 100,
        'currency' => PAYPAL_CURRENCY,
        'returnUrl' => PAYPAL_RETURN_URL,
        'cancelUrl' => PAYPAL_CANCEL_URL,
    ))->send();

    if ($response->isRedirect()) {
        $response->redirect(); // this will automatically forward the customer
    } else {
        // not successful
        dd($response->getMessage());
    }
} catch(Exception $e) {
    dd($e);
}

function dd($content)
{
    echo  "<pre>";
        var_dump($content);
    echo "</pre>";
} 

在我的config.php中，我已经完成了

<?php

    require_once "vendor/autoload.php";
     
    use Omnipay\Omnipay;
     
    define('CLIENT_ID', 'my-client-id');
    define('CLIENT_SECRET', 'my-secret-id');
     
    define('PAYPAL_RETURN_URL', 'localhost/paypalwp/success.php');
    define('PAYPAL_CANCEL_URL', 'localhost/paypalwp/cancel.php');
    define('PAYPAL_CURRENCY', 'USD'); // set your currency here
     
     
    $gateway = Omnipay::create('PayPal_Rest');
    $gateway->setClientId(CLIENT_ID);
    $gateway->setSecret(CLIENT_SECRET);
    $gateway->setTestMode(true); //set it to 'false' when go live 

在我的success.php中，我已经完成了

<?php

    require_once 'config.php';
     
    // Once the transaction has been approved, we need to complete it.
    if (array_key_exists('paymentId', $_GET) && array_key_exists('PayerID', $_GET)) {
        $transaction = $gateway->completePurchase(array(
            'payer_id'             => $_GET['PayerID'],
            'transactionReference' => $_GET['paymentId'],
        ));
        $response = $transaction->send();
     
        if ($response->isSuccessful()) {
            // The customer has successfully paid.
            $arr_body = $response->getData();
     
            $payment_id = $arr_body['id'];
            $payer_id = $arr_body['payer']['payer_info']['payer_id'];
            $payer_email = $arr_body['payer']['payer_info']['email'];
            $amount = $arr_body['transactions'][0]['amount']['total'];
            $currency = PAYPAL_CURRENCY;
            $payment_status = $arr_body['state'];
     
            echo "Payment is successful. Your transaction id is: ". $payment_id;
        } else {
            echo $response->getMessage();
        }
    } else {
        echo 'Transaction is declined';
    }

并且在cancel.php中，我有一个简单的html布局，表示用户已取消付款

但是当我尝试这段代码时，它给了我这个错误"Invalid request - see details"

知道为什么要这么做吗？