處理未定義的變量

Question

我有一個變量$product，$categories，$most_views，$show，$check，$checkforid該指數函數。

public function index() 
    { 
     $products=Product::where(['status'=>'1'])->orderBy('most_viewed','desc')->with('category')->get(); 
     $categories=Category::all(); 
     $mostviews=Product::where(['status'=>'On sale'])->orderBy('most_viewed','desc')->limit(10)->get(); 
     $show=Product::orderBy('most_viewed','desc')->with('category') 
                ->with('user') 
                ->with('productbrand.brand')           
                ->first(); 

     if(Auth::check()) 
     { 
      $check=Watchlist::where(['user_id'=>Auth::user()->id])->get()->toArray(); 
      foreach($check as $che) 
      { 
       $checkforid[]=$che['product_id']; 
      } 
     }  

     return View('product.index',['products'=>$products,'mostviews'=>$mostviews,'show'=>$show,'checkforid'=>$checkforid,'categories'=>$categories]); 
    } 

如果這些變量的亙古不變的存在，

return View('product.index',['products'=>$products,'mostviews'=>$mostviews,'show'=>$show,'checkforid'=>$checkforid,'categories'=>$categories]); 

總會有一個錯誤未定義的變量和整個索引頁會受到影響。所以我想跳過不存在的變量。這是最好的解決方案是什麼？

直到現在，我已經初始化所有變量爲null.so，如果任何變量不存在null傳遞。這是一個好習慣嗎？

public function index() 
    { 
     $products=null; 
     $show=null; 
     $check=null; 
     $checkforid=null; 
     $mostviews=null; 
     $categories=null; 

     $products=Product::where(['status'=>'1'])->orderBy('most_viewed','desc')->with('category')->get(); 
     $categories=Category::all(); 
     $mostviews=Product::where(['status'=>'On sale'])->orderBy('most_viewed','desc')->limit(10)->get(); 

    ... 
} 

Answer 1

據我所知，你唯一的問題是$checkforid。只是初始化爲空數組：

$checkforid = []; 
if(Auth::check()) 
{ 
    ... 
    $checkforid[]= ... 
    ... 
} 

一個好的IDE會發出警告，告訴你什麼「$checkforid可能無法定義」。

Answer 2

所有的變量都會有東西，我敢打賭問題是在視圖中。所以，僅僅做這樣的事情在一個觀點：

@if (count($products) > 0) 
    @foreach ($products as $product) 
    .... 
@endif 

或者，如果你想檢查是否定義的變量，並且有一個值：

@if (!empty($someVar)) 

Answer 3

檢查參數設置使用，

$data = array(); 
if(isset($products)) 
    $data['products'] = $products; 
... 
return View('product.index', $data); 

Answer 4

有這種解決方案也是如此，這在我看來是更優雅：

$products=Product::where(['status'=>'1'])->orderBy('most_viewed','desc')->with('category')->get(); 
    $categories=Category::all(); 
    $mostviews=Product::where(['status'=>'On sale'])->orderBy('most_viewed','desc')->limit(10)->get(); 
    $show=Product::orderBy('most_viewed','desc')->with('category') 
               ->with('user') 
               ->with('productbrand.brand')           
               ->first(); 
    $view = View('product.index',['products'=>$products,'mostviews'=>$mostviews,'show'=>$show,'categories'=>$categories]); 
    if(Auth::check()) 
    { 
     $check=Watchlist::where(['user_id'=>Auth::user()->id])->get()->toArray(); 
     foreach($check as $che) 
     { 
      $checkforid[]=$che['product_id']; 
     } 
     $view->with('checkforid', $checkforid); 
    }  

    return $view;