Warning: mysqli_connect(): Error while reading greeting packet. PID=20 in /var/www/includes/database.php on line 15

Warning: mysqli_connect(): (HY000/2006): MySQL server has gone away in /var/www/includes/database.php on line 15

Fatal error: Uncaught Error: Call to a member function set_charset() on bool in /var/www/includes/database.php:16 Stack trace: #0 /var/www/includes/database.php(10): MySQLDatabase->open_connection() #1 /var/www/includes/database.php(68): MySQLDatabase->__construct() #2 /var/www/includes/initialize.php(11): require_once('/var/www/includ...') #3 /var/www/index.php(2): require_once('/var/www/includ...') #4 {main} thrown in /var/www/includes/database.php on line 16