Why a variable function?

It makes the code, just that much modular and D.R.Y (don't repeat yourself). Which as an application grows, becomes quite important.

Here is probably a poor example, but lets say I have a function to calculate the amount of tax that someone owes me. Now lets say I use that function no matter which state the person is in, they owe me the same amount of tax, but I have a different function to calculate the shipping charges.

At this stage, I can have my two functions tax and shipping next to each other, and referred to later in the code. But now tax laws have changed for some states, and I have to adapt for that. So now what I can do, is write a new function next to the existing functions that take into account the new tax requirements, and instead of going through my code and replacing each and every function call to my old tax function for each state, I just simply reassign the variable the function references, and once I do that, the code should work fine. Doesn't matter if I referenced the function 23 times to calculate the tax for a user of that state, I can just make one change, and all 23 function calls get updated to use the new, correct function.

Again, that's probably not the best example, but the idea is that you only want to have to set something, somewhere, one time. This makes it far more easy and less error prone to make changes to the code later. Hope that helps.

Kevin Korte , thanks for your explanation. In your example:

function tax(){return tax owed};
$tax2 = 'tax';
$tax2() + updated tax

but then why not juse use

$tax2 = tax() + updated tax

What's the purpose?

AHHH. Wow. Ok, I think I am beginning to understand this. Thank you.

So far, thanks to your example, I understand that I can set a function = $somevariable and then use that variable to call the function like this:

$somevariable();

and this will call the function.

$somevariable is defined higher up in my code and all I would need to do is change the code inside of the "{ code here }" part of the function and then the calculations would reflect that one change I set equal to $somevariable because I am calling the variable function instead using the same function over and over and having to change it wherever it may be in the code.

Is that right?

Ah, that is making sense now. Thank you. Making the variable function equal to the new variable function you made so that function gets called instead of the old one.