我確實對這段代碼有問題，這是使用的模型    <?phpnamespace App;use Illuminate\Database\Eloquent\Model;class Navigation extends Model{    protected $table = "navigation" ;    protected $primaryKey = "navi_id";    public function PrimaryNavigation()    {        return $this->hasMany(PrimaryNavigation::class);    }}這就是查詢的方式        <?php    namespace App\Http\Controllers;    use App\Navigation;    use App\PrimaryNavigation;    use Illuminate\Http\Request;    class NavigationController extends Controller    {        /**         * Display a listing of the resource.         *         * @return \Illuminate\Http\Response         */        public function index()        {             $mainNavi = Navigation::with('PrimaryNavigation')->get() ;             return view('dump')->with('data',$mainNavi);        }}?>每當我嘗試打印來自此查詢的結果時，它永遠不會顯示相關表的正確輸出。當我打印輸出時它顯示正確的結果但是當我試圖打印出相關的表數據時它只顯示 NULL 值@foreach($data as $single) {{dd($single)}}</br>@endforeach此代碼顯示正確的輸出{"navi_id":8,"navi_name":"fouad","navi_route":"\/fouad","navi_sort":0,"navi_created_at":"2019-09-23 02:21:24.000000","navi_last_update":"2019-09-23 02:21:29.000000","primary_navigation":[{"primary_navi_id":5,"navigation_navi_id":8,"primary_navi_name":"tamer","primary_navi_route":"\/tamer","primary_navi_created_at":"2019-09-23 02:28:38.000000","primary_navi_last_update":"2019-09-23 02:28:40.000000","primary_navi_sort":0},{"primary_navi_id":13,"navigation_navi_id":8,"primary_navi_name":"momo","primary_navi_route":"\/momo","primary_navi_created_at":"2019-09-23 14:44:13.000000","primary_navi_last_update":"2019-09-23 14:44:15.000000","primary_navi_sort":0}]}但是當我試圖只顯示相關表時，它給出了 null@foreach($data as $single) {{dd($single->primary_navigation)}}</br>@endforeach