مشکل در متد checkout در بخش payment

با عرض سلام 

در BasketController متد زیر مشکل دارد ، متغیر order مقدار null رو برمیگردونه
 

BasketController.php codes :

 private $basket;
    private $transaction;
    public function __construct(Basket $basket , Transaction $transaction)
    {
        $this->middleware('auth')->only(['checkoutForm','checkout']);
        $this->basket = $basket;
        $this->transaction = $transaction;

    }
public function checkout(Request $request)
    {
        $this->validateForm($request);
        $order =  $this->transaction->checkout();
        if(!is_null($order)){
            return redirect()->route('home')->with('success', __('payment.your order has been registered', ['orderNum' => $order->id]));
        }
        return 'Order is Empty';
    }
-----------------------------------------------------
Transaction.php codes :

 public function checkout()
    {
        DB::beginTransaction();
        try{
            $order = $this->makeOrder();
            $payment = $this->makePayment($order);
            DB::commit();
        }catch(\Exception $e){
            DB::rollBack();
            return null;
        }
        if ($payment->isOnline()) {
            $this->gatewayFactory()->pay($order);
        }
        $this->completeOrder($order);
        return $order;
    }

 private function makeOrder()
    {
        $order = Order::create([
            'user_id' => auth()->user()->id,
            'code' => bin2hex(str_random(16)),
            'amount' => $this->basket->subTotal()
        ]);
        $order->products()->attach($this->products());
        return $order;
    }
    private function makePayment($order)
    {
        return Payment::create([
            'order_id' => $order->id,
            'pay_method' => $this->request->pay_method,
            'amount' => $order->amount,
        ]);
    }

private function gatewayFactory()
    {
        $gateway = [
            'saman' => Saman::class,
            'pasargad' => Pasargad::class
        ][$this->request->gateway];

        return resolve($gateway);
    }
 private function completeOrder($order)
    {
        $this->normalizeQuantity($order); 
        event(new OrderRegistered($order));
        $this->basket->clear();
    }