获取访问者IP地址

    static public function getip()
	{
		if (getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknown"))
		{
			$ip = getenv("HTTP_CLIENT_IP");
		}
		else if (getenv("HTTP_X_FORWARDED_FOR") && strcasecmp(getenv("HTTP_X_FORWARDED_FOR"), "unknown"))
		{
			$ip = getenv("HTTP_X_FORWARDED_FOR");
		}
		else if (getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR"), "unknown"))
		{
			$ip = getenv("REMOTE_ADDR");
		}
		else if (isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], "unknown"))
		{
			$ip = $_SERVER['REMOTE_ADDR'];
		}
		else
		{
			$ip = "";
		}
		return($ip);
	}