Classes of the Yii framework usually extend from one of the two base classes [[yii\base\Object]] or [[yii\base\Component]].
These classes provide useful features that are added automatically to all classes extending from them.
The [[yii\base\Object|Object]] class provides a[configuration and property feature](../api/base/Object.md).
The [[yii\base\Object|Object]] class provides the[configuration and property feature](../api/base/Object.md).
The [[yii\base\Component|Component]] class extends from [[yii\base\Object|Object]] and adds
[event handling](events.md) and [behaviors](behaviors.md).
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@@ -89,7 +89,7 @@ All classes, interfaces and traits are loaded automatically at the moment they a
Yii's autoloader works according to [PSR-4](https://github.com/php-fig/fig-standards/blob/master/proposed/psr-4-autoloader/psr-4-autoloader.md).
That means namespaces, classes, interfaces and traits must correspond to file system paths and file names accordinly, except for root namespace paths that are defined by an alias.
For example, if the standard alias `@app` refers to `/var/www/example.com/` then `\app\models\User` will be loaded from `/var/www/example.com/app/models/User.php`.
For example, if the standard alias `@app` refers to `/var/www/example.com/` then `\app\models\User` will be loaded from `/var/www/example.com/models/User.php`.
Custom aliases may be added using the following code:
