It's been a long time but I have finally got round to trying your suggestion. I added php -q as you suggested but it has just thrown up the following error:
Warning: Failed opening 'C:\Web Site\wwwrootphp -q \cgi-bin\orderForm.php' for inclusion (include_path='') in Unknown on line 0
This is the line I added to my page:
<!--#exec cgi="php -q /cgi-bin/orderForm.php" -->