I converted the database from utf8 to utf8mb4
After I change from core/database.php
array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8;', to utf8mb4
the website is running hard and many features such as logging(parsererror), chat does not work(does not display messages and people, loads to infinity, no errors).
it doesn't even work if I change it back, but I have backup
How fix ?