Just thought I would post this in case anyone happens to use CI with the FoxyCart datafeed... CI may munge up your rc4crypt'ed urlencoded POST data and leave you with gibberish when you decrypt it.
While I later got CI to pass is through -- I originally just moved the decrypt and DB instert of the raw XML to a little external helper script. Then a call into a CI script in the main system does all the parsing and heavy lifting.
Not sure if anyone else out there in the foxy world uses CI -- but in just in case, thought this might save someone a few hours of hair pulling.
(And...once I have the CI library for fully handling the datafeed cleaned up, I'll update with a link, in case it might useful.)