framework/web/Session.php
public function removeAllFlashes()
    {
        $counters = $this->get($this->flashParam, []);
        foreach (array_keys($counters) as $key) {
            unset($_SESSION[$key]);
        }
        unset($_SESSION[$this->flashParam]);
    }
public function removeAllFlashes()
    {
        $counters = $this->get($this->flashParam, []);
        foreach (array_keys($counters) as $key) {
            unset($_SESSION[$key]);
        }
        unset($_SESSION[$this->flashParam]);
    }
Removes all flash messages.
Note that flash messages and normal session variables share the same name space.
If you have a normal session variable using the same name, it will be removed
by this method.
@see getFlash()
@see setFlash()
@see addFlash()
@see removeFlash()