So I thought that I could make a "multi-threaded" (but not really) program in php by using stream_set_blocking. Well, the things I need to do simultaneously involve calling popen on external programs and then reading the data and doing something with them.
Well, popen doesn't work with stream_set_blocking(..., false), so I can't do things that way. Unfortunately, I've spent a week or two setting up the framework for all this (so it would be easy and convenient) but now I find it can't be done.
Oh well, time to give up on trying to do that in PHP then, and just buckle down to doing it in C++ (the original version is in C++, but frankly, I just don't want to maintain that code anymore, no choice now though).