https://blog.wongcw.com/2021/07/02/php-8-1%e6%96%b0%e5%8a%9f%e8%83%bd%e5%88%9d%e6%8e%a2%ef%bc%9a%e6%b7%bb%e5%8a%a0enums-fsync%e5%92%8cfibers%e7%ad%89%e6%ad%a3%e5%bc%8f%e7%89%8811%e6%9c%88%e7%99%bc%e5%b8%83/