php script stays the same. use this c-script snippet to upload a file... afaik the file must be in the same directory as the exe file.

Code:

dll_handle = dll_open("GSHTTP.dll");
HTTP_Create(0);
HTTP_PostFile(0, "http://here's the URL/upload.php", "myfile.foo");
while (HTTP_IsWorking(0)) {
    wait(1);
}
HTTP_Free(0);
dll_close(dll_handle);