Warning: mysqli::__construct(): Error while reading greeting packet. PID=54 in /var/www/html/index.php on line 2

Fatal error: Uncaught mysqli_sql_exception: MySQL server has gone away in /var/www/html/index.php:2 Stack trace: #0 /var/www/html/index.php(2): mysqli->__construct('mysql', 'appuser', Object(SensitiveParameterValue), 'app') #1 {main} thrown in /var/www/html/index.php on line 2