function isMobile() {
        $objAgent =& Net_UserAgent_Mobile::singleton();
        if (Net_UserAgent_Mobile::isError($objAgent)) {
            return false;
        } else {
            return $objAgent->isDoCoMo() || $objAgent->isEZweb() || $objAgent->isVodafone() || $this->isSmartPhone();
        }
    }

    function isSmartPhone($userAgent = null)
    {
        if (is_null($userAgent)) {
            $userAgent = $_SERVER['HTTP_USER_AGENT'];
        }

        if (preg_match('!^iPhone!', $userAgent) || preg_match('!^iPod!', $userAgent) || preg_match('!^iPad!', $userAgent) || preg_match('!^Android!', $userAgent)) {
            return true;
        }

        return false;
    }

    function isDoCoMo($userAgent = null)
    {
        if (is_null($userAgent)) {
            $userAgent = $_SERVER['HTTP_USER_AGENT'];
        }

        if (preg_match('!^DoCoMo!', $userAgent) || preg_match('!^iPhone!', $userAgent) || preg_match('!^iPod!', $userAgent) || preg_match('!^iPad!', $userAgent) || preg_match('!^Android!', $userAgent)) {
            return true;
        }

        return false;
    }