EXIF Data

I am futzing around in PHP writing some routines to extract EXIF Data. In my old camera days(Oly 2020, 4040, and early 5050) I shot mostly in JPG. All the EXIF Data is as I want(F-Stop, Aperture, etc) and comes out when I loop over the EXIF data. In the 5050, this is not the case, it seems. F-Stop, Aperture, etc seem to be buried in the binary somewhere. Not only that, but I have recently been using the Adobe PS CS, which seems to save a lot of data in XML format. Anybody know of some useful functions for parsing this data(both binary from the Oly format and XML from the Adobe format)? Thanks in advance! As a last resort I may just use libraries, but was hoping to do this one by hand...