Notice: Undefined variable: mysqli in D:\Brockmann\incl\terminabfrage.inc.php on line 38

Fatal error: Uncaught Error: Call to a member function query() on null in D:\Brockmann\incl\terminabfrage.inc.php:38 Stack trace: #0 D:\Brockmann\incl\terminabfrage.inc.php(96): isLocked(1534603164, '36c6294c') #1 D:\Brockmann\gk\terminabfrage.php(2): require('D:\\Brockmann\\in...') #2 {main} thrown in D:\Brockmann\incl\terminabfrage.inc.php on line 38