Nested functions... Why?

[blueman378]

Hi guys.

 

I was looking into a way to tidy up my code and i came across the idea of nested functions: a quick google found this:

 

When you define a function within another function it does not exist until the parent function is executed. Once the parent function has been executed, the nested function is defined and as with any function, accessible from anywhere within the current document. If you have nested functions in your code, you can only execute the outer function once. Repeated calls will try to redeclare the inner functions, which will generate an error.

 

why would you need nested functions?

 

any examples of them being used?

[trq]

I've never found any need for them.

[blueman378]

so are nested functions something thats coded into php to support them, or is it just something that was there by way of other pieces that they just left?

[genericnumber1]

It's kind of a primitive way of procedural encapsulation I guess... I've certainly never found a use for it. I'm sure they put it in, it's doubtful it was just a byproduct of the compiler, other programming languages have them as well.

[PravinS]

I have used nested function to generate multilevel dynamic menu.

[blueman378]

I have used nested function to generate multilevel dynamic menu.

 

could i see an example code?

 

is it sort of a case as each level is a different function if the upper levels dont get declared then the lower ones dont need to exist?

[redarrow]

It seems that one advantage is that you could declare the same function in different contexts.

 

Consider a dynamic function call: $functionname="functionone";

 

Now if you want, you can call: $functioname(); myecho();

 

let us say you have defined

<?php
function functionone(){
..function myecho(){
....echo "I am one";
..}
}

function functiontwo(){
..function myecho(){
....echo "I am two";
..}
}`
?>

Now you can call myecho(), and you'll get "i am one". Change the original $functionname to "functiontwo" and the same myecho() call will now spit out "I am two".

 

[genericnumber1]

Yeah, if only I could find a use for that procedural polymorphism? no thanks, I'll stick with my objects.

[blueman378]

lol so basically its just another case of we can put it in so we will?

[genericnumber1]

Well other people put it in, SOMEONE must swear by them somewhere, I just don't know who the heck the guy is.

[Yesideez]

Freaky!

 

In almost 30 years of programming I've never had the need to do anything like this and never knew this existed!