Fatal error: Uncaught TypeError: mysqli_query(): Argument #1 ($mysql) must be of type mysqli, null given in /var/www/services/QMS/database.php:122 Stack trace: #0 /var/www/services/QMS/database.php(122): mysqli_query() #1 /var/www/services/QMS/get_doctors.php(36): database->getDoctorList() #2 /var/www/services/QMS/get_doctors.php(43): IP_QMS->getDoctor() #3 {main} thrown in /var/www/services/QMS/database.php on line 122