https://blog.toright.com/posts/2871/%e5%88%a5%e8%ae%93%e4%b8%8d%e5%b7%a5%e4%bd%9c%e7%9a%84-ipv6-%e5%bd%b1%e9%9f%bf-php-%e7%9a%84%e7%b6%b2%e8%b7%af%e9%80%a3%e7%b7%9a%e9%80%9f%e5%ba%a6%ef%bc%88dns-%e8%a7%a3%e6%9e%90%e9%8c%af%e8%aa%a4