Basic FDF data is easy to create using native PHP; you don't need Adobe's FDF Toolkit. I wrote a function for this purpose called forge_fdf(). You can download it from:
http://www.pdfhacks.com/forge_fdf/
I created it for my book, PDF Hacks. An example of forge_fdf() in action can be viewed online:
http://pdfhacks.com/form_session/form_session-1.1/
Download the full code for this online example from:
http://pdfhacks.com/form_session/
Note how the PDF form data is submitted back to the server via POST rather than FDF. No need to parse FDF.
Cheers-
Sid Steward