thinkphp sets DB_CHARSET to utf8mb4

tp3.2.3 database configuration 'DB_CHARSET'=> 'utf8mb4', execution error. As follows

<code>SQLSTATE[HY000] [2019] Can't initialize character set utf8mb4 (path: /usr/share/mysql/charsets/)
错误位置

FILE: /data1/www/htdocs/733/ecampus/3/ThinkPHP/Library/Think/Db/Driver.class.php 　LINE: 109
</code>

If you don’t use tp, you can use native sql ‘set names utf8mb4’ and it will execute without any problem.
What went wrong? Please fix it! Thank you!