I posted about what the data looks like when you submit a form using an HTTP Submit Button, but there are other ways of submitting forms.
I’ve created a Submit Comparison PDF that has a few fields on it, and buttons for the four different types of data submission that Acrobat supports.
These are: XDP, PDF, XML, and URL-encoded.
URL-encoded is what the HTTP Submit Button does; to use one of the other formats, drop a Button onto your form, set the Control Type to Submit, and then you can use the Submit tab on the Object Inspector to control how the data is submitted.
Submitting in XDP format gives you XML data that includes an xfa:data model, as well as an execEvent node that identifies which button the user pushed to submit the form. This provides the most data.
Submitting XML gives you the same data that you’d get if you emailed the filled out form data from Reader – it’s an XML packet with a chunk of friendly human-readable text that describes how to submit the data. The form data you get is the same as what you get with the XDP format, but without the xfa wrappers.
Try out the PDF file I linked above – the Submit button posts to my dump.php script so you can see what actually got submitted.