protected function initialize()
    {
        if ($this->initialized) {
            // Already initialized
            return true;
        }

        if (session_status() !== PHP_SESSION_NONE) {

            if (isset($_SESSION[$this->key]) && is_array($_SESSION[$this->key])) {
                // Get the token collection from the session, if we got any
                $this->tokens = $_SESSION[$this->key];
            }

            $this->initialized = true;

        } else {

            throw new CsrfSessionException('A session must be started before the Csrf library can be used');

        }
    }