Laravel : Update Stock Value After Order Placement - laravel

Question

I want to update stock value when order will place. The challenge is that the products have different attributes place in the attribute table.
Small, Medium, Large, Extra large
I want to update the product attribute stock respectively when order is place. For example when user place order user selected products like
product_id = 1 size Small quantity is 7
So 7 quantity must be decrement from the product attribute size Small column.
Checkout
// checkout
public function checkout(Request $request)
{
if ($request->isMethod('post')) {
$data = $request->all();
DB::beginTransaction();
// Get cart details (Items)
$cartItems = Cart::where('user_id', Auth::user()->id)->get()->toArray();
foreach ($cartItems as $key => $item) {
# code...
$cartItem = new OrdersProduct;
$cartItem->order_id = $order_id;
$cartItem->user_id = Auth::user()->id;
// Get products details
$getProductDetails = Product::select('product_code', 'product_name', 'product_color')->where('id', $item['product_id'])->first()->toArray();
$cartItem->product_id = $item['product_id'];
$cartItem->product_code = $getProductDetails['product_code'];
$cartItem->product_name = $getProductDetails['product_name'];
$cartItem->product_color = $getProductDetails['product_color'];
$cartItem->product_size = $item['size'];
$getDiscountedAttrPrice = Product::getDiscountedAttrPrice($item['product_id'], $item['size']);
$cartItem->product_price = $getDiscountedAttrPrice['final_price'];
$cartItem->product_qty = $item['quantity'];
$cartItem->save();
// Want to Update the Product Attribute Table Stock
$item = new ProductsAttribute;
$item->where('product_id', '=', $item['product_id'], 'size', '=', $item['size'])->decrement('stock', $request->quantity);
}
// Insert Order Id in Session variable for Thanks page
Session::put('order_id', $order_id);
DB::commit();
}
}
When i run this code it shows me an error
InvalidArgumentException
Non-numeric value passed to decrement method.
When i enter value directly like decrement('stock', 7) it shows and error
Illuminate\Database\QueryException
SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '`product_id` is null' at line 1 (SQL: update `products_attributes` set `stock` = `stock` - 7, `products_attributes`.`updated_at` = 2021-05-01 17:18:30 where size `product_id` is null)
i search alot but yet not find any solution. Please any one help

Answer 1

Just change the update query and make it simple and clean. The rest of the code is fine.
// Want to Update the Product Attribute Table Stock
$product_attribute = ProductsAttribute::where(['product_id' => $item['product_id'], 'size' => $item['size']])->first();
if($product_attribute){
$stock = $product_attribute->stock - (int) $request->quantity;
$product_attribute->update(['stock' => $stock]);
}

Answer 2

you have to warp it in an array or use two of wheres better and understandable
$item->where([
['product_id', '=', $item['product_id']],
['size', '=', $item['size']],
])->decrement('stock', (int) $request->quantity);
Or like this:
$item->where('product_id', $item['product_id'])
->where('size', $item['size'])
->decrement('stock', (int) $request->quantity);