yii\base\ActionFilter::beforeFilter PHP Method

    public function beforeFilter($event)
    {
        if (!$this->isActive($event->action)) {
            return;
        }
        $event->isValid = $this->beforeAction($event->action);
        if ($event->isValid) {
            // call afterFilter only if beforeFilter succeeds
            // beforeFilter and afterFilter should be properly nested
            $this->owner->on(Controller::EVENT_AFTER_ACTION, [$this, 'afterFilter'], null, false);
        } else {
            $event->handled = true;
        }
    }