You need not to use mutator to set the Auth:id() for new model instance. Checkout the Eloquent event to set Auth::id() as user_id during the creation of new model instance.

• For Post model code sample will

  <?php namespace App\Providers; use App\User; use Illuminate\Support\ServiceProvider; class AppServiceProvider extends ServiceProvider { /** * Bootstrap any application services. * * @return void */ public function boot() { Post::creating(function ($post) { $post->user_id = Auth:id(); }); } /** * Register the service provider. * * @return void */ public function register() { // } }

Don't Forget to register the service provider