Fatal error: Uncaught TypeError: mysqli_ping(): Argument #1 ($mysql) must be of type mysqli, null given in /var/www/vhosts/duffer.in/session/session.php:331 Stack trace: #0 /var/www/vhosts/duffer.in/session/session.php(331): mysqli_ping() #1 /var/www/vhosts/duffer.in/session/session.php(11): session->_mysqli_ping() #2 /var/www/vhosts/duffer.in/dbcon.php(26): session->__construct() #3 /var/www/vhosts/duffer.in/desktop/header.php(2): include_once('...') #4 /var/www/vhosts/duffer.in/desktop/index.php(1): include_once('...') #5 /var/www/vhosts/duffer.in/index.php(8): include('...') #6 {main} thrown in /var/www/vhosts/duffer.in/session/session.php on line 331