I have a MySQL dump, which I tried to restore with:
mysql -u"username" -p"password" --host="127.0.0.1" mysql_db < mysql_db
ERROR 1115 (42000) at line 3231: Unknown character set: 'utf8mb4'
/*!50003 SET character_set_client = utf8mb4 */ ;
/*!50003 SET character_set_results = utf8mb4 */ ;
/*!50003 SET collation_connection = utf8mb4_general_ci */ ;
Your version does not support that character set, I believe it was
5.5.3 that introduced it. You should upgrade your mysql to the version you used to export this file.
The error is then quite clear: you set a certain character set in your code, but your mysql version does not support it, and therefore does not know about it.
utf8mb4 is a superset of utf8
so maybe there is a chance you can just make it utf8, close your eyes and hope, but that would depend on your data, and I'd not recommend it.