Warning: Undefined variable $connect in /volume2/web/iteach4u/htdocs/2017/exammaterials/downloadLayer.php on line 16

Fatal error: Uncaught TypeError: mysqli_query(): Argument #1 ($mysql) must be of type mysqli, null given in /volume2/web/iteach4u/htdocs/2017/exammaterials/downloadLayer.php:16
Stack trace:
#0 /volume2/web/iteach4u/htdocs/2017/exammaterials/downloadLayer.php(16): mysqli_query(NULL, 'select * from e...')
#1 {main}
  thrown in /volume2/web/iteach4u/htdocs/2017/exammaterials/downloadLayer.php on line 16