src/actions/RedirectAction.php
public function getUrl()
    {
        if ($this->_url instanceof Closure) {
            return call_user_func($this->_url, $this);
        }

        return $this->_url ?: Yii::$app->request->referrer;
    }
public function getUrl()
    {
        if ($this->_url instanceof Closure) {
            return call_user_func($this->_url, $this);
        }

        return $this->_url ?: Yii::$app->request->referrer;
    }
public function getUrl ( ) { if ( $ this -> _url instanceof Closure ) { return call_user_func ( $ this -> _url , $ this ) ; } return $ this -> _url ? : Yii :: $ app -> request -> referrer ; }
Collects the URL array, executing callable functions.

@return string|array default return to previous page (referer)
Collects the URL array executing callable functions .