Submit button doesn't show in wordpress only

Hi,

I am working with some signup.php code and have placed this php code into a wordprses page:

<?php
require_once(‘signup.php’);
?>

This does a great job of showing the signup form directly in the wordpress theme/page.

However, when I hit submit, the page automatically redirects to an /index.php url which pulls up a blank theme page instead of the signup.php submit follow-up message. When the form itself is not embedded into a wordpress page (as described above) but only linked to on a wordpress page, signup.php still remains after submit it pressed and I can see the follow-up message.

What do I need to do to keep the index.php from intervening and allow the signup.php to continue to run through its script while having everything be in the wordpress theme? Is this an issue of headers or something I need to add to the index.php page to keep it from taking over the script?

Thank you.