Fatal error: Uncaught TypeError: implode(): Argument #2 ($array) must be of type ?array, string given in /home/httpd/html/prog-crs.ust.hk/program/print_result.php:661 Stack trace: #0 /home/httpd/html/prog-crs.ust.hk/program/print_result.php(661): implode() #1 {main} thrown in /home/httpd/html/prog-crs.ust.hk/program/print_result.php on line 661