Recursively sort array to levels - php

Question

I've been working on a site that uses binary mlm system.
Illustration here
So I have a two tables in database, users anad relationships. There is ID and personal data columns in users. Relationships has 4 columns: ID, parentID, childID, pos. Where pos is either left or right.
I have succesfully written a function that recursively lists all children of given pid (parentID). However I need to sort it in levels (for display and calculation purposes).
I have an array of children of user ID = 1:
Array
(
[0] => Array
(
[id] => 2
[parentID] => 1
[pos] => l
)
[1] => Array
(
[id] => 4
[parentID] => 2
[pos] => l
)
[2] => Array
(
[id] => 8
[parentID] => 4
[pos] => l
)
[3] => Array
(
[id] => 5
[parentID] => 2
[pos] => p
)
[4] => Array
(
[id] => 3
[parentID] => 1
[pos] => p
)
[5] => Array
(
[id] => 6
[parentID] => 3
[pos] => l
)
[6] => Array
(
[id] => 7
[parentID] => 3
[pos] => p
)
)
Now I have function named get_levels that returns an multidimensional array that should look like this:
Array
(
[0] => Array
(
[0] => Array
(
[id] => 2
[parentID] => 1
[pos] => l
)
[1] => Array
(
[id] => 3
[parentID] => 1
[pos] => p
)
)
[1] => Array
(
[0] => Array
(
[id] => 4
[parentID] => 2
[pos] => l
)
[1] => Array
(
[id] => 5
[parentID] => 2
[pos] => p
)
[2] => Array
(
[id] => 6
[parentID] => 3
[pos] => l
)
[3] => Array
(
[id] => 7
[parentID] => 3
[pos] => p
)
)
ETC.
)
Here's the function:
function get_levels($pid,$level, $level_id){
$children = children_array($pid,1);
if (sizeof($children) > 0):
foreach ($children as $child):
if ($child["parentID"] == $pid):
get_levels($child["id"], $level, $level_id+1);
$level[$level_id][] = $child;
endif;
endforeach;
endif;
return $level;
}
function children_array($pid, $depth) returns the children ... for $depth = 1 it returns immediate children (0 or 1 or 2), for $depth = 0 it returns all children
Can anyone help me with this function? I think the function works, however I don't know how to recursively use and add to array.

Answer 1

Looks like you're using a data structure within the wrong context. It's a binary tree, yet it's represented into a multilevel array which in short doesn't define its boundaries and rules of use.
When using the tree, I would use something like a Node class that has two children, left and right. Iterating through the tree would be piece of cake, inserting/deleting/editing into it is easily done depending on which set of rules you want to follow. When storing the tree, I would use some kind of Ahnentafel list which can easily be done in a relational database.
I would in no way mix both iteration and storage processes because if I change the rules of storage, I might also have to change the rules of iteration and vice versa.