https://blog.wongcw.com/2018/11/16/%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8php-%e6%93%b4%e5%b1%95memcached-%e7%9a%84%e9%95%b7%e9%80%a3%e6%8e%a5%e6%a8%a1%e5%bc%8f/