yiisoft/yii2 — pull request #1491 by egorpromo (2013-12-12 14:31:39+00:00)
Title: Eliminating constant

In yii\base\Controller we have `Yii::$app->trigger(Application::EVENT_BEFORE_ACTION, $event);`. It is hard and complicated to look at yii\base\Application.php every time. This event is used only once. There is no need to use constant. It is possible to do the same thing in simple way. So I think we can eliminate redundant information to ease our work.