Autoloading

Note: This chapter is under development.

All classes, interfaces and traits are loaded automatically at the moment they are used. There's no need to use include or require. It is true for Composer-loaded packages as well as Yii extensions.

Yii's autoloader works according to the PSR-4 standard. That means namespaces, classes, interfaces and traits must correspond to file system paths and file names accordingly, 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/models/User.php.

Custom aliases may be added using the following code:

Yii::setAlias('@shared', realpath('~/src/shared'));

Additional autoloaders may be registered using PHP's standard spl_autoload_register.