Run some calculation and then update data in Laravel 5.2 - php

Question

Here is a very simple store method of a product controller. I do some calculation and then store the data into the database. But while updating data I have to run this calculations again and then have to save the data.
I tried several ways but I get nothing but error messages as I'm new in Laravel. How can I write the proper update method?
public function store(Request $request)
{
//vat and profit calculations
$vat = $request->vat;
$buying_price = $request->buying_price;
$selling_price = $request->selling_price;
$total_price = $buying_price+($buying_price*$vat/100);
$profit = $selling_price-$total_price;
$product = Products::create([
'product_name' => $request->product_name,
'buying_price' => $request->buying_price,
'selling_price' => $request->selling_price,
'vat' => $request->vat,
'total_price' => $total_price,
'profit' => $profit,
]);
return redirect("Product/{$product->id}");
}
Update method (which is not working as I expect):
public function update(Request $request, $id)
{
$vat = $request->vat;
$buying_price = $request->buying_price;
$selling_price = $request->selling_price;
$total_price = $buying_price+($buying_price*$vat/100);
$profit = $selling_price-$total_price;
$product = Products::findOrFail($id);
$product = Products::update([
'product_name' => $request->product_name,
'buying_price' => $request->buying_price,
'selling_price' => $request->selling_price,
'vat' => $request->vat,
'total_price' => $total_price,
'profit' => $profit,
]);
return redirect("Product/{$product->id}");
/* Basic update system but this does not update the total_price and profit column
$input = $request->all();
$product = Products::findOrFail($id);
$product->update($input);
return redirect("Product/{$product->id}"); */
}

Answer 1

Should be like this ...
public function update(Request $request, $id){
$vat = $request->vat;
$buying_price = $request->buying_price;
$selling_price = $request->selling_price;
$total_price = $buying_price+($buying_price*$vat/100);
$profit = $selling_price-$total_price;
$product = Products::findOrFail($id);
$product->product_name = $request->product_name;
$product->product_category_id = $request->product_category_id;
$product->product_type_id = $request->product_type_id;
$product->product_description = $request->product_description;
$product->product_weight = $request->product_weight;
$product->buying_price = $request->buying_price;
$product->selling_price = $request->selling_price;
$product->vat = $request->vat;
$product->total_price = $total_price;
$product->profit = $profit;
$product->in_stock = $request->in_stock;
$updated_product = $product->save();
if(isset($updated_product) && $updated_product != '') {
return redirect("Product/".$id);
}
}

Answer 2

Please Try This.
public function update(Request $request, $id)
{
$vat = $request->vat;
$buying_price = $request->buying_price;
$selling_price = $request->selling_price;
$total_price = $buying_price+($buying_price*$vat/100);
$profit = $selling_price-$total_price;
$product = Product::where('id', $id)->first();
$product->product_name = $request->product_name;
$product->buying_price = $request->buying_price;
$product->selling_price = $request->selling_price;
$product->vat = $request->vat;
$product->total_price = $total_price;
$product->profit = $profit;
$product->save();
return redirect("Product/{$product->id}");
/* Basic update system but this does not update the total_price and profit column
$input = $request->all();
$product = Products::findOrFail($id);
$product->update($input);
return redirect("Product/{$product->id}"); */
}