Ask the multi handle if there are any messages/informationals from the individual transfers. Messages may include informationals such as an error code from the transfer or just the fact that a transfer is completed.
Repeated calls to this function will return a new result each time, until a
FALSE is returned
as a signal that there is no more to get at this point. The integer pointed to with
msgs_in_queue will contain the number of remaining messages after this
function was called.
The data the returned resource points to will not survive calling curl_multi_remove_handle().
A cURL multi handle returned by curl_multi_init().
Number of messages that are still in the queue