Since you can't autoload functions who aren't members of a class, you must include/require the file on every request, or otherwise include the file whenever you use those methods. PHP projects have, generally, abstracted the thinking about "what file does this thing come from?" by now - via the autoloader - which, as I said, doesn't work with functions. So functions, annoyingly, create a leak in the abstraction that otherwise allows us to forget about exactly what files our code lives in.
As an aside, to me, it also raises questions regarding the design of your code (how do I inject mock methods?). But that's hard to know without seeing it (if the methods are simple enough, perhaps there's just no need to mock them in your tests).
I encapsulate "helper" or "utility" logic in objects, e.g. RandomGenerator with a getRandom, which can be amazing when it comes to testing, and lets me forget about include/require'ing files.
As an aside, to me, it also raises questions regarding the design of your code (how do I inject mock methods?). But that's hard to know without seeing it (if the methods are simple enough, perhaps there's just no need to mock them in your tests).
I encapsulate "helper" or "utility" logic in objects, e.g. RandomGenerator with a getRandom, which can be amazing when it comes to testing, and lets me forget about include/require'ing files.