Fatal error: Uncaught TypeError: mysqli_close(): Argument #1 ($mysql) must be of type mysqli, null given in /var/www/services/QMS/database.php:153 Stack trace: #0 /var/www/services/QMS/database.php(153): mysqli_close() #1 /var/www/services/QMS/get_patient.php(54): database->closeDB() #2 {main} thrown in /var/www/services/QMS/database.php on line 153