/**
  * Display the specified resource.
  *
  * @param  int  $id
  * @return \Illuminate\Http\Response
  */
 public function show($id)
 {
     $product = Product::find($id)->toArray();
     $additional = null;
     if ($product['category'] == 'laptop') {
         $additional = Laptop::where('id_product', $id)->first()->toArray();
     } elseif ($product['category'] == 'book') {
         $additional = Book::where('id_product', $id)->first()->toArray();
     }
     $product = array_merge($product, $additional);
     $head = array('title' => $product['name']);
     $data = array('head' => $head, 'product' => $product);
     return view('product.show', $data);
 }