Warning: fopen(notes.txt): Failed to open stream: Permission denied in /hotlz/websites/asw/kalendar/src/saveNotes.php on line 6

Warning: Undefined variable $notes in /hotlz/websites/asw/kalendar/src/saveNotes.php on line 7

Fatal error: Uncaught TypeError: fwrite(): Argument #1 ($stream) must be of type resource, false given in /hotlz/websites/asw/kalendar/src/saveNotes.php:7
Stack trace:
#0 /hotlz/websites/asw/kalendar/src/saveNotes.php(7): fwrite(false, NULL)
#1 {main}
  thrown in /hotlz/websites/asw/kalendar/src/saveNotes.php on line 7