private function _isHttps()
    {
        if (!empty($_SERVER['HTTP_X_FORWARDED_PROTO'])) {
            return ($_SERVER['HTTP_X_FORWARDED_PROTO'] === 'https');
        } elseif (!empty($_SERVER['HTTP_X_FORWARDED_PROTOCOL'])) {
            return ($_SERVER['HTTP_X_FORWARDED_PROTOCOL'] === 'https');
        } elseif ( isset($_SERVER['HTTPS'])
            && !empty($_SERVER['HTTPS'])
            && strcasecmp($_SERVER['HTTPS'], 'off') !== 0
        ) {
            return true;
        }
        return false;

    }