public function getUserLogin()
    {
        // Is a session mechanism available?
        if (!session_id()) {
            if ($this->sessionManager) {
                $this->sessionManager->start();
            } else {
                throw new MoufException("The session must be initialized before checking if the user is logged. Please use session_start().");
            }
        }
        
        if (isset($_SESSION[$this->sessionPrefix.'MoufUserLogin'])) {
            return $_SESSION[$this->sessionPrefix.'MoufUserLogin'];
        } else {
            foreach ($this->authProviders as $provider) {
                /* @var $provider AuthenticationProviderInterface */
                $login = $provider->getUserLogin($this);
                if ($login) {
                    return $login;
                }
            }
        }
        return null;
    }