mysqli::__construct(): Server sent charset (255) unknown to the client. Please, report to the developers in

这个问题都是由于ＰＨＰ版本过低＋ＭＹＳＱＬ版本过高引起的

ＭＹＳＱＬ８.０　＋　版本引入了新字符集　ｕｔｆ８ｍｂ４　

把老的ｕｔｆ８　ａｌｉａｓ至　ｕｔｆ８ｍｂ３

而老的ＰＨＰ的ＭＹＳＱＬＮＤ模块没有包含新增的字符集

所以会出现

Error when using mysqli:

PHP Warning:  mysqli::__construct(): Server sent charset (255) unknown to the client. Please, report to the developers in ... on line 3

Error when using PDO_MYSQL:

Connection failed: SQLSTATE[HY000] [2054] Server sent charset unknown to the client. Please, report to the developers

解决办法很简单，　升级新的PHP版本即可

官方 https://bugs.php.net/bug.php?id=74461

有写的

[2018-05-02 12:13 UTC] [email protected]

Should be fixed as of 7.0.19, 7.1.5, and 7.2.0. Anyone confirm?

[2018-05-02 17:37 UTC] macleo at outlook dot com

Should be fixed as of 7.0.19, 7.1.5, and 7.2.0. Anyone confirm? - yes

所以7.0+的版本 基本都OK