Fedex Freight API Fix (php)

I'm developing a PHP system to obtain shipping rates from some LTL Freight carriers, I already finished some of them and they are working OK, but Fedex Freight not. I'm having problems with the SOAP request since I can't build correctly the array for the request, Fedex send back I'm having errors in the request. I don't understand the docs at Fedex website and I don't know how to debug php or xml response for this kind of errors. I need someone with Fedex API experience that can check and fix (in my own php class) the parameters I'm using to build the array for the request to the SOAP FedEx Rate Service (Quotes), I would send you the source code I have, as well as the description of the parameters array that I need. Note: Is mandatory to do this in my own class in order to match my others implementations. You only need to fix the array building part to match the Fedex docs and get a correct response from the webservice.