This code uses the PEAR HTTP request.
setBasicAuth("johndoe", "foo");
$req->setMethod(HTTP_REQUEST_METHOD_POST);
$req->addPostData("video_id", $video_id);
$req->addPostData("format_id", "31");
if (!PEAR::isError($req->sendRequest())) {
echo $req->getResponseBody(); // XML response
}
?>