Cílová třída laravel neexistuje
Uncomment this line in app>>provider>>RouteServiceProvider.php file
// protected $namespace = 'App\\Http\\Controllers';
Cílová třída [Controller] neexistuje.
//accessing any function in the controller (this is web.php file)
use App\Http\Controllers\PostsController;
Route::get('/post', 'App\Http\Controllers\PostsController@index');