Why can Yii::app()->request->urlReferrer be empty in yii?

Question

Yii

Good afternoon,
I put the following construction into the controller action (users/registration):

if(!$role || ($role < 1 || $role > 2))
        {

            Yii::app()->user->setFlash('error','Пожалуйста укажите роль');
            die(Yii::app()->request->urlReferrer);
            $this->redirect(Yii::app()->request->urlReferrer);
        }

Yii::app()->request->urlReferrer didn't return the URL of the page I came from, what could be the problem?

Answer 1

The client is not obliged to give you his Referrer, this is "voluntary" information.
If you open a bookmarked page or open a new tab, there may not be a referrer.
Or the browser just "wanted".