Thanks, Matt. Basically, what I'm doing is going through Frontier/UserTalk functions - many of which are documented at:
http://docserver.userland.com
And rewriting the functions as PHP class functions.
If you are using the OPML Editor, you can test out UserTalk functions by hitting Ctrl + ; (or Cmd + ; on the Mac) and putting in your functions. Variables are without prefix (no $ etc.). If you are writing in the Quick Script window, end your lines with a semi-colon (but if you are writing in an outline, you just press enter).
If you want more advice, just drop me an email. The "frontier-kernel" mailing list on Yahoo Groups is a good place to ask for help.