Yii2 Get current action in controller

You can get current action name by:

Yii::$app->controller->action->id

And get the controller name with this one:

 Yii::$app->controller->id;

Note: Remember that these will only work after the application has been initialized. Possible use: inside a controller action/ inside a model or inside a view

Reference: Class yii\web\Controller

You should use beforeAction() event instead of init().

Also you can simply use $this because it contains current controller.

public function beforeAction($action)
{
    if (parent::beforeAction($action)) {
        if ($this->action->id == 'lang') {
            Url::remember();
        }

        return true; // or false if needed
    } else {
        return false;
    }
}

if use Yii2 in view - try this: $this->context->action->id;