dll_handle = dll_open("GSHTTP.dll");
HTTP_Create(0);
HTTP_Post(0,"http://here's the URL/upload.php", poster2);
while (HTTP_IsWorking(0)) {
    wait(1);
}
HTTP_Free(0);
dll_close(dll_handle);

<?php
// the php library can't know that you want your file attached to 'datei',
// since it does not parse the html code from above. so we need a plain php
// script that handles upload of anonymously uploaded files.
if (count($_FILES) && $_FILES[0]['error'])
{
	$filename = $_FILES[0]['name'];
	if (move_uploaded_file($_FILES[0]['tmp_name'], $filename)) {
                  echo "SUCCESS";
        } else {
                  echo "FAILURE";
        }
} else {
        echo "FAILURE";
}
?>

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);