Question

I imagine this is a fairly common requirement for people when it comes to building any kind of application that relies on sorting and displaying data in categories – any CMS/Forums/Carts etc and I’ve been tearing my hair out trying to think of a way to show all categories and their children to no avail – the best I’ve managed is while loop within while loop (however many levels I think I may require) but this defeats the point of programming in my opinion, it needs to be effortlessly extensible.

So, given:

Category 1
-Sub cat
-Sub cat
--Sub sub cat
--- Sub sub cat
-- Sub sub cat
-Sub cat
Category 2
-Sub cat
-Sub cat
--Sub sub cat
---sub sub sub cat
----sub sub sub sub cat
-sub cat
Category 3
-Sub cat

Database fields: ID Name ParentIDS

How would you go about echoing each of the categories in their hierarchy from a database?

I’d post my code, but obviously its massive, given the long-hand way of nesting loops.

I’ve thought about writing bits of code that find the ‘depth’ of the category tree but that still isn’t cutting it.. ideas?

Answer 1

The structure you’re talking about is essentially a tree. Iterating over a tree is relatively simple if you use recursion. I don’t know what database access code you’re using, but you should be able to extrapolate accordingly from the following psuedocode:

function iterate_tree(arr) {
    foreach (item in arr) {
        print item;
        iterate_tree(item.children);
    }
}

In english, that means print an item in the list, then print its children, and once all children (and their children) have printed, move on to the next item in the list.