I mean, yes, I do provide two methods f1 and f2, but whenever the client app needs both f1 and f2, I want to batch them in a single HTTP request. The sever still calls the handlers of f1 and f2 respectively. My purpose to do it is to save HTTP connections (1 connection for both f1 and f2 instead of 2 for f1 and f2).
If anyone in doubt googles "restful batch", there are pretty some discussion on this topic.
Any way, since Slim is a framework, I wish it keeps the subRequest API because it's useful even though the Slim developers don't think so.