<FORM name="xx" id="form_id" action="https://www.salesforce.com/servlet/servlet.WebToLead?encoding=UTF-8"  onsubmit="xx;" method="POST"> 
<input type="hidden" name="oid" value="xx">
<!--<input type="hidden" name="debug" value="1">
<input type="hidden" name="debugEmail" value="xx"> -->
<input type="hidden" name="retURL" value="http://www.sithankyou.php"/>

Currently my development setup is as follows

User registers using the landing page. The landing page connects to salesforce to create a lead. Salesforce throws out a thankyou page using the URL I had supplied during the creation of web.

The issue is

The thank you page has a PHP script which sends out an email to the registered user. I am not able to access the fields from the landing page

eg: $email = $_POST[email]; // where email is a field in the landing page which I am trying to access in the thankyou page.

How do I go about resoving this issue?

Do I need to include the email field in the query string in thankyou page URL?

Is there a possiblity to access this field via salesforce?

Thanks !

<FORM name="xx" id="form_id" action="https://www.salesforce.com/servlet/servlet.WebToLead?encoding=UTF-8"  onsubmit="xx;" method="POST"> 
<input type="hidden" name="oid" value="xx">
<!--<input type="hidden" name="debug" value="1">
<input type="hidden" name="debugEmail" value="xx"> -->
<input type="hidden" name="retURL" value="http://www.sithankyou.php"/>