public function index()
 {
     $message = null;
     $cartitems = null;
     if (!Session::get('cart_id')) {
         $message = "You have nothing in your cart";
         return view('cart.index', compact('message', 'cartitems'));
     } else {
         $cart_id = Session::get('cart_id');
         $cart = Cart::whereId($cart_id)->firstOrFail();
         $cartitems = $cart->cartitems()->get();
         // total up the cart
         $grandtotal = 0;
         foreach ($cartitems as $item) {
             $grandtotal += $item->price_total;
         }
         $cart->total = $grandtotal;
         $cart->save();
         // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
         return view('cart.index', compact('message', 'cartitems', 'cart'));
     }
 }