I see your goal now...
I can show you the C-code of playfid, but I dont think it's easy to port it to php. I think it's easier to rewrite from scratch in php.
You can generate the main page ( root playlist ) by reading fid 100. The format of a playlist-file is documented at smu's site if I remember correctly.
You can read the metainfo by reading fid 101, which is an ascii list of all attributes.
one hint : to force the downloaded file to be named with a different filename in php :

header ("Content-Type: application/octet-stream");

header ("Content-Disposition: attachment; filename=myfilename.mp3");

Frank van Gestel