A new function httprl_is_backround_callback_capable() has been added. You can now disable background callbacks on the configuration page. If background callbacks are disabled, httprl_queue_background_callback() will return NULL. If a 'background_callback' is set for a normal http request, it will be transformed into a 'callback' and then ran. Disabling backround callbacks should only been done if you can not get them to work on your server.