How to import a new class in a new folder

Hi all:

I am a newer for Yii2。i had a new folder components with one file Controller.php


    namespace app\controllers;

    use Yii;

    use yii\web\controller as YWController;

    class Controller extends YWController{}

but in another folder such as "controllers" :

    namespace app\controllers;

    class DefaultController extends Controller{}

  run and some mistake appeared as follow:


 PHP Fatal Error – yii\base\ErrorException

 Class 'app\controllers\Controller' not found



because of psr-4

class ‘app\controllers\Controller’ must be in path ‘@app/controller[size=“6”]s[/size]/Controller.php’

so, add ‘s’ to folder name