Extract equally from X queues to one queue with Y elements
First off, you're code looks nice, but it can be improved in places:


I don't see why:

        $totSmsToSend = count($smsToSend);



Is indented so far, you should fix that. There's quite a few elements that have been over indented.


Your constant use of the word Sms like so, seems a bit silly, as it as an acronym, you should stick to SMS or sms but don't mix cases.
$tot, You shouldn't leave out two characters, just for the purpose of slimming when it makes it much less readable.
Your code seems really forced, so I think it could be improved in the method it goes about doing.


Your solution really just sounds like basic division:


Y / X, rounded down to a whole number
For leftover positions in Y queue, transfer X(1), X(2), ... X(X) and go through until you fill up the queue.