I have been doing quite a bit of processing of RETSfeeds over the last few years. To use a RETSfeed, you really do need a library to help simplify the processing, and you need to know what is available in the RETSfeed. Here are my suggestions …
Visit www.retsmd.com when you have the address of your RETSfeed and the login information. retsmd.com provides a very simple method for examining the RETSfeed to see what classes and variables are available to you on the RETSfeed.
If you are looking for a useful library to use for processing, Troy Davission has a good, free library available … PHRETS. This library is quick to access, easy to use and very useful. I have used it on several projects and it seems to blend with my PHP processing very nicely.