the confirm page pdf you sent has nothing in it, it is blank.
the headers already sent error happens because of blank space or other output to the page.
it could be a blank space at the end of a closing php block:
a blank lines between a closing php block and an opening php block:
or a comment:
<!-- commnet here -->
the error points to the problem being at line 7 or 8.
see this thread for details on troubleshooting this error: