Question

private function find_children ($parent_id, $children, &$result)
{              
    foreach ($children as $c)
    {            
        if ($c->parent_comment_id == $parent_id)
        {                
            $result[] = $c;
            $this->find_children($c->id, $children, $result);            
        }            
    }
    return;        
}

The above function is supposed to take a starting parent id and recursively go through an array of children nodes (really just an object with a unique id and a parent id) sorting them so that each node comes directly after it’s parent (see below for sample data).

But for some reason, the function doesn’t execute as I expect. I have the following data for testing.

id: 1 pid: 0 (the initial parent which is not in the children array passed to func. problem?)
id: 2 pid: 1
id: 3 pid: 2
id: 4 pid: 1
id: 5 pid: 3
id: 6 pid: 5
id: 7 pid: 4
id: 8 pid: 3

and want the following array returned:
1, 4, 7, 2, 3, 8, 5, 6

But instead, I get:
1, 2, 3, 5, 6

which, while they’re in the right order, a few are missing.

I have not had the need to do recursion in many years, so likely I am missing something obvious, although not so obvious to myself.

In case anyone is wondering, or if it matters, I’m trying to build a q&a commenting system where every post can have multiple replies.

Thus:

initial post 
-reply to initial post #1
--reply to reply
-reply to initial post #2
-- reply to above
--- reply to above
--reply to #2

Answer 1

I think you’re looking for something like a Nested Set Tree. It should do what you want.