public static function request_header($name)
    {
        if (function_exists('getallheaders')) {
            $hdrs = array_change_key_case(getallheaders(), CASE_UPPER);
            $key  = strtoupper($name);
        }
        else {
            $key  = 'HTTP_' . strtoupper(strtr($name, '-', '_'));
            $hdrs = array_change_key_case($_SERVER, CASE_UPPER);
        }

        return $hdrs[$key];
    }