Using custom request and custom redirect with Contact Form 7

Question

I have several sites that I want to link back to the main site which hosts the contact form (using contact form 7).

I would like to capture the request parameter "site-url" on incoming links to the contact form.

Then when the user submits the form, I would like to redirect them back to the site specified in the site-url.

Any ideas if this is possible with contact form 7?

I would also like to add a special field in the contact form which would insert the site-url into the email that i get so that I know which site they were referred from.

Answer 1

Contact Form Page

<?php
session_start();

$redirect = $_GET['site-url'];
$_SESSION['redirect'] = $redirect;

POST Contact Form Page

<?php
session_start();

$redirect = $_SESSION['redirect'];

mail('[email protected]','Contact Form',$redirect);

header("Location: {$redirect}");
exit();