I think there's a lot of this going around. If its in a professional level, it belongs on serverfault. If its something that's unlikely to be on a production server - its for personal development use , you could probably ask on SU. Small scale server stuff is a grey area, and at some point, I think SU and SF need to sit down and work out something on this.
However, "what have you tried?" will be asked anywhere. SE isn't a replacement for research effort. I also note the question on programmers.se lacks details.
Tell us a story. Tell us why you really need two versions of PHP, and mention what you've considered or tried so far. Make us see why this install needs to be portable (and what is portable here? Between installs on identical systems with the same OS? any linux system?). Make the question something your audience will look at and go oooh, and its less likely to be closed. You need to show both that you've tried to solve the problem, and add more cowbell to the question to get attention.
I've not tried it myself, but a quick google search suggested this as a method - so clearly this isn't an unanswerable question, but one where a little more research could get you started. You will then have a better chance of asking a question to fix minor issues and not have it closed.