The FedEx documentation can be quite extensive & complicated. I'm working with Shippo (https://goshippo.com). We provide an easy-to-use FedEx REST API and a PHP client library. Let me know if I can help with further questions!
You can get access to the FedEx API by logging into your FedEx account and clicking on the "Developer Resource Center" link in the footer. The direct link is http://www.fedex.com/us/developer/web-services/index.html. You can download the documentation and sample code from there.