Why is there a "Class not found" error in Yii2?

Question

Yii

Good day! I made a module in one Yii2 project, I needed it in the second one, I just copied it to this project, but when I try to open it, I get the error "Class 'backend\modules\media_library\models\MediaLibrary' not found".
In the model that lies along the path "backend/modules/media_library/models" it says "namespace backend\modules\media_library\models;"
The controller says "use backend\modules\media_library\models\MediaLibrary;"
Tell me what could be the problem? If you need any more information, please write in the comments.
Thanks in advance for the replies!

Answer 1

PSR-4 Learn the
materiel - https://github.com/codedokode/pasta/blob/master/ph...
PS Have you registered the namespace of the module in the config?

$config = [
    // ...
  'modules' => [
    'admin' => [
                         'class' => 'app\modules\admin\Module',
                ],
  ],
    // ...
];