Creating bulk read job with callback - no data posted to callback url?

Creating bulk read job with callback - no data posted to callback url?

I am creating a bulk read job with bulk api and use a URL as callback.

The documentation says: 'The Bulk Read Job's details is posted to this URL...'.

But there is no data posted to the URL (in php, the $_POST array is empty).

The callback page is called (I wirte a timestamp to a logfile), and when I attach some get parameter to the URL, the $_GET array is filled.

Is this intentional, or should there be some data posted (at least the bulk read job id)?