SamReidHughes

Right, but usually when you want to make something secure (like a jail cell) you only have to think in 3 dimensions (and we all should know how perilously foolhardy it is to think in only 2!). If you make your jail cell out of PHP, the PHP interpreter might at a future time change the material your bars are made of, or reconfigure the lock so that a clothespin can open your current design, or consider your walls to be nonexistent because you've used the wrong number of equal signs, or change the behavior of some obscure molecule in a way never previously documented. You can't just build your jail cell so that it works in this universe, you have to build it so that it works in every universe, even ones you have no way of knowing the existence of.