获取客户端IP

	/**
	 * 获取客户端IP地址
	 *
	 * @return string
	 */
	public static function getClientIp()
	{
		if (!empty($_SERVER["HTTP_CLIENT_IP"]))
			return $_SERVER["HTTP_CLIENT_IP"];

		if (!empty($_SERVER["HTTP_X_FORWARDED_FOR"]))
			$proxy_ip = $_SERVER["HTTP_X_FORWARDED_FOR"];
		elseif (($tmp_ip = getenv("HTTP_X_FORWARDED_FOR")))
			$proxy_ip = $tmp_ip;
		else
			$proxy_ip = '';
		
		if ('' !== $proxy_ip)
		{
			if (false === strpos($proxy_ip, ','))
				return $proxy_ip;
			
			foreach (explode(',', $proxy_ip) as $curr_ip)
			{// 处理可能有多级代理的情况
				if (false === stripos($curr_ip, 'unknown'))
					$curr_ip = ltrim($curr_ip);
				else
					continue;
				
				if (0 === strpos($curr_ip, '192.168.'))
					continue;	// 内网IP
				if (0 === strpos($curr_ip, '10.'))
					continue;	// 内网IP
				if (0 === strpos($curr_ip, '172.16.'))
					continue;	// 内网IP
				
				return $curr_ip;
			}
		}

		if(!empty($_SERVER["REMOTE_ADDR"]))
			return $_SERVER["REMOTE_ADDR"];
		elseif(($retvl = getenv("HTTP_CLIENT_IP")))
			return $retvl;
		elseif(($retvl = getenv("REMOTE_ADDR")))
			return $retvl;
		else
			return '0.0.0.0';
	}