|I don't think I've ever tried this, but there's nothing in the PHP wrapper that would preclude doing it. From the code's perspective it's just another URL and it doesn't care that it's a local machine.|
There might be something in curl itself, but I can't imagine what. If you're running a linux box, you might try the interactive curl command and see what happens (or running cygwin on a Windoze box). Curl could conceivably be optimizing accesses to your local machine through the localhost interface or somesuch, but I've never heard of that being the case.
Sorry I can't be of more help.