Submit PDF to server as XFDF. What exactly is getting passed?

Ok so I followed this tutorial to get the PDF submitting to HTML but it seems like a backwards way to do it.

http://koivi.com/fill-pdf-form-fields/tutorial.php

I would like to submit the data as XML so I can then easily map it to a model.

The Adobe documentation is probably the worse I've ever seen. I followed the submit button documentation but that doesn't tell me anything. What exactly is getting passed to the server?

What POST parameter am I looking for? What name? What does it look like. These questions seem basic but I 开发者_如何学运维don't see it anywhere. Thanks.

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XFDF format is described here: http://partners.adobe.com/public/developer/en/xml/xfdf_2.0.pdf
The body of the POST request contains the XFDF data.