Let's say that there is an eccentric multi-trillionare who made his fortune by coding a very popular service in PHP. He knows it very well, and has such a love for it that he makes a rather unorthodox decision:
He starts a new "space tourism" company, hiring the smartest people in the world and pumping in countless trillions of dollars into giving them access to the best hardware and parts and materials that money can buy. There is just one small "catch": it has to run PHP CLI for all the calculations.
That is, they can freely choose whatever existing OS, commercial or not, and the best hardware that money can buy, but it has to run the unmodified stock PHP CLI (latest stable release), and it has to use only CLI PHP scripts for all the calculations.
They are allowed to fully vet the code, compile it locally, exclude as many or as few of the included base extensions as they wish, etc., but they cannot code their own interpreter or make changes to the code which powers PHP CLI itself.
What, exactly, is it about this that is so "crazy"? I realize that it probably is, but I don't understand why. I frankly cannot remember PHP ever "calculating the wrong number" or even crashing on me, especially not when I'm not involving a bunch of fragile external software as well. The "core" of PHP appears to me to be very reliable, and I would definitely not be skeptical to running PHP CLI on the "master computer" for a major corporation or bank.
Of course, space travel gives the phrase "mission critical" a whole new meaning, as any error could result in death, but does a space craft really ever have to have the answer so quickly that it matters if it takes a few more milliseconds? Because isn't that what we are talking about in terms of performance? Just about any math problem I've ever thrown onto PHP has been "instantly" (to my eyes) calculated every time. If the space crafts of the 1960s were able to go to the moon and back, how could PHP CLI running on some ultra-stable commercial or custom OS with a modern, expensive space computer as the bare metal have any problems whatsoever?
Am I somehow over-simplying things somehow? Not thinking about some crucial detail?
Of course, the engineers are allowed to make a bunch of redundant virtual machines and/or physical computers that all do the same thing and communicate with each other. They just all have to do all the actual work and calculations with PHP CLI scripts.
Admittedly, I would not dare to travel in this space craft myself, but then again, so wouldn't I no matter what it runs!
Also, the "ground control" part also is bound by the same constraint, so that they don't "cheat" and simply calculate everything down on Earth and then send the space craft the instructions directly. Having said that, they aren't required to do every calculation related to the mission on the space ship, as long as the space ship is able to function independently and both go into space (let's say to the moon) and return to Earth without depending on analogue 1960s equipment which bypasses the PHP CLI requirement or something like that.
Essentially, what I'm wondering is: What about using PHP CLI is so fundamentally incompatible with this? Even if you're gonna reply that it doesn't do secure floating point or something, can't they just use integers like they always did in old video games when they didn't have FPUs, or use the "BC Math" base extension in PHP to get "true floats"?
I am very much looking forward to the insightful and clarifying answers to this, and I hope I won't see any mindless PHP bashing.