Php Laravel Braintree\Configuration:：需要设置merchantId（或者需要将accessToken传递给Braintree\Gateway）

请帮助我，在正确安装braintree版本“5.3”后，我尝试在我的laravel项目上使用paypal支付，但它不起作用 这让我犯了一个错误：需要设置Braintree\Configuration:：merchantId（或者需要将accessToken传递给Braintree\Gateway）
这是我的：
checkout.blade.php

@extends('layouts.default')                             
@section('content')           
 //code                 
@endsection                 
@section('extra-js')
  
    <script src="https://js.braintreegateway.com/web/dropin/1.13.0/js/dropin.min.js"></script>
    <script>

            (function(){
            var form = document.querySelector('#paypal-payment-form');
            var client_token = "{{ $paypalToken }}";

            braintree.dropin.create({
              authorization: client_token,
              selector: '#bt-dropin',
              paypal: {
                flow: 'vault'
              }
            }, function (createErr, instance) {
              if (createErr) {
                console.log('Create Error', createErr);
                return;
              }

              // remove credit card option
              var elem = document.querySelector('.braintree-option__card');
              elem.parentNode.removeChild(elem);

              form.addEventListener('submit', function (event) {
                event.preventDefault();

                instance.requestPaymentMethod(function (err, payload) {
                  if (err) {
                    console.log('Request Payment Method Error', err);
                    return;
                  }

                  // Add the nonce to the form and submit
                  document.querySelector('#nonce').value = payload.nonce;
                  form.submit();
                });
              });
            });

        })();
    </script>
@endsection                             

public function index()
    {
        $gateway = new \Braintree\Gateway([
            'environment' => config('services.braintree.environment'),
            'merchantId' => config('services.braintree.merchantId'),
            'publicKey' => config('services.braintree.publicKey'),
            'privateKey' => config('services.braintree.privateKey')
        ]);

        
            $paypalToken = $gateway->ClientToken()->generate();
       

        
        return view('checkout')->with([
            'paypalToken' => $paypalToken,
            ]);
    }                                  

当然，我把它添加到了我的config services.php中

 'braintree' => [
        'environment' => env('BT_ENVIRONMENT', 'sandbox'),
        'merchantId' => env('BT_MERCHANT_ID'),
        'publicKey' => env('BT_PUBLIC_KEY'),
        'privateKey' => env('BT_PRIVATE_KEY'),
    ],