"Trying to get property 'price' of non-object" - php

Question

I had a Laravel script installed, Now When the user fills in the new order form and makes an order for ordering, will be displayed:
"Trying to get property 'price' of non-object"
The error is for usercontroller and this line:
" $price = ($request->quantity * $servicePrice->price) / 1000;"
This part code is for new order in usercontroller:
public function newOrder()
{
$categories = Category::where('status', 1)->orderBy('name')->get();
return view('user.newOrder', compact('categories'));
}
public function getPack(Request $request)
{
$items = Service::where('category_id', $request->id)->where('status', 1)->orderBy('name')->get();
return $items;
}
public function getPackDetails(Request $request)
{
$items = Service::findOrFail($request->id);
return $items;
}
public function storeNewOrder(Request $request)
{
$this->validate($request, [
'category' => 'required',
'service' => 'required',
'link' => 'required',
'quantity' => 'required',
]);
$service = Service::where('category_id', $request->category)->where('id', $request->service)->first();
$servicePrice = ServicePrice::where('category_id', $request->category)->where('service_id', $request->service)->where('user_id', Auth::id())->first();
$item = new Order();
$user = User::findOrFail(Auth::id());
$transaction = new Transaction();
if ($request->quantity >= $service->min && $request->quantity <= $service->max) {
$price = ($request->quantity * $servicePrice->price) / 1000;
if ($user->balance >= $price) {
$item->category_id = $request->category;
$item->service_id = $request->service;
$item->user_id = Auth::id();
$item->service_no = $service->service_id;
$item->order_no = 0;
$item->link = $request->link;
$item->quantity = $request->quantity;
$item->price = $price;
$item->status = 'Pending';
$item->start_counter = 0;
$item->remains = $request->quantity;
$item->order_through = 'Web';
$item->save();
$user->balance = $user->balance - $price;
$user->save();
$transaction->user_id = Auth::id();
$transaction->amount = $price;
$transaction->user_balance = $user->balance;
$transaction->type = 1;
$transaction->trx = str_random(12);
$transaction->save();
send_email($user->email, $user->name, 'Order Placed Successfully', 'Your ' . $request->quantity . ' ' . $service->name . ' has been placed successfully.');
session()->flash('success', 'Order request send successfully');
return back();
} else {
session()->flash('alert', 'Insufficient Balance');
return back();
}
} else {
session()->flash('alert', 'Quantity should be within ' .
$service->min . ' to ' . $service->max);
return back();
}
}

Answer 1

Most probably the problem comes from this line:
$servicePrice = ServicePrice::where('category_id', $request->category)->where('service_id', $request->service)->where('user_id', Auth::id())->first();
If a query does not return any result from the database, the code will return null.
A good practice is to check if the result is null and you should handle it.
That means, before you use the $servicePrice, you need to check if it contains anything:
if(!$servicePrice){ //same result: if($servicePrice == null) {
//`$servicePrice==null`, so you should handle the error here - throw an exception or return
}
//your code here
$servicePrice = ServicePrice::where('category_id', $request->category)->where('service_id', $request->service)->where('user_id', Auth::id())->first();
Also, the authenticated user can be retrieved directly from:
$user = Auth::user();
If the visitor is not authenticated, $user will be null, for the same reason than the previous.
if(!$user){
//the user is NOT authenticated
} else {
//the user is authenticated
}