Use the ::class notation

Author: pespantelis

config/api.php

@@ -185,7 +185,7 @@
     |
     */
 
-    'transformer' => env('API_TRANSFORMER', 'Dingo\Api\Transformer\Adapter\Fractal'),
+    'transformer' => env('API_TRANSFORMER', Dingo\Api\Transformer\Adapter\Fractal::class),
 
     /*
     |--------------------------------------------------------------------------
@@ -202,7 +202,7 @@
 
     'formats' => [
 
-        'json' => 'Dingo\Api\Http\Response\Format\Json',
+        'json' => Dingo\Api\Http\Response\Format\Json::class,
 
     ],