Gocardless Webhook implementation in Laravel

Question

I'm testing using Webhooks for the first time. I want to set up a Webhook (using GoCardless.com).

I have created a acces token and Webhook endpoints in my sandbox account. URL-http://test.com/remote_gocardless

My route is,

   Route::post('/remote_gocardless','remotegocardlessController@remote')->name('remote');

Controller is,

namespace App\Http\Controllers;
use App\Http\Controllers\Controller;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Input;

class remotegocardlessController extends Controller
{


public function remote()
{

  $token ="tunnelnew";

  $raw_payload = file_get_contents('php://input');

   $headers = getallheaders();
   $provided_signature = $headers["Webhook-Signature"];
   $calculated_signature = hash_hmac("sha256",$raw_payload,$token);
   if ($provided_signature == $calculated_signature) {

  $payload = json_decode($raw_payload, true);


    foreach ($payload["events"] as $event) {


 switch ($event["resource_type"]) {
  case "mandates":
  process_mandate_events($event);
    break;
  case "payments":
    process_payment_events($event);
    break;

   case "subscriptions":

   process_subscription_events($event);
   break; 

   }
 }


  header("HTTP/1.1 200 OK");
 } else {
   header("HTTP/1.1 498 Invalid Token");
  }


}


 }

response in sandbox account is like, 500 Internal Server Error.

Is there is any other code i have to add for implementing webhook in laravel? Can we give url as http instead of https?