Basically when you install multiple PHPs with Homebrew, they don't end
up on PATH anywhere - you can brew link one of them, but that overwrites
any other PHPs you might have previously linked.
Other platforms, such as Ubuntu, package their PHPs such that a binary
called something like php7.4 ends up on PATH. This is a much more
helpful approach, since you can specifically invoke the necessary
version of PHP by adding a version suffix.
This script does the same thing for Homebrew-installed PHPs. Pretty
simple.
