CI_Session::unset_userdata PHP Method

    public function unset_userdata($key)
    {
        if (is_array($key)) {
            foreach ($key as $k) {
                unset($_SESSION[$k]);
            }
            return;
        }
        unset($_SESSION[$key]);
    }

 function unset_userdata($newdata = array(), $path = false, $regex = false)
 {
     if (is_string($newdata)) {
         if ($path) {
             foreach (array_keys($this->userdata) as $key) {
                 if (strpos($key, $newdata . '/') === 0) {
                     unset($this->userdata[$key]);
                 }
             }
         }
         if ($regex) {
             foreach (array_keys($this->userdata) as $key) {
                 if (preg_match($newdata, $key)) {
                     unset($this->userdata[$key]);
                 }
             }
         }
     }
     parent::unset_userdata($newdata);
 }