Illegal mix of collations (utf8mb4_general_ci,IMPLICIT) and (utf8_general_ci,COERCIBLE) for operation

2022/01/01 15:01:34 [error] 27751#0: *92883 FastCGI sent in stderr: "PHP message: SQLSTATE[HY000]: General error: 1267 Illegal mix of collations (utf8mb4_general_ci,IMPLICIT) and (utf8_general_ci,COERCIBLE) for operation '='" while reading response header from upstream, client: ***.9.208.203, server: www.xtboke.com, request: "GET /message.html HTTP/2.0", upstream: "fastcgi://unix:/tmp/php-cgi-72.sock:", host: "www.xtboke.com"

第一步：如下

第二步：找到数据库配置文件database.php，做如下修改：
'charset' => 'utf8mb4'