the headers already sent error because of blank space or other output between closing php tags "?>" and opening php tags "<?php"
this output can be a blank line:
or a blank space at the end of the closing tag:
or a comment:
<!-- html comment here -->
the error is reporting the output at line 5 or 6:
if you are not able to spot the issue, send a copy of the php page in a zip archive.