On Thu, Jan 12, 2012 at 12:14 PM, David Skinner
<[email protected]> wrote:
> I've looked around the internet and haven't quite found what I'm looking
> for. I have a flat array with each element containing an 'id' and a
> 'parent_id'. Each element will only have ONE parent, but may have multiple
> children. If the parent_id = 0, it is considered a root level item. I'm
> trying to get my flat array into a tree. The other samples I have found
> only only copy the element to the parent, but the original still exists.
>
> Each element of the starting array is read from a separate XML file which
> is created by a 3rd party app. The file itself will have '0' as the value
> for parent_id if it doesn't have a parent. The keys are actually strings.
>
> My starting array:
For what it's worth, here's what I thought might work as we were
discussing this in IRC:
1. Start by making a list of all the children for each parent:
$lists = array();
foreach ($startingarray as $k => $v) {
$lists[$v['parent_id']][$k] = $v;
}
That should give you something like this:
Array
(
[0] => Array
(
[_319_] => Array
(
[id] => 0
[parent_id] => 0
)
[_320_] => Array
(
[id] => _320_
[parent_id] => 0
)
[_323_] => Array
(
[id] => _323_
[parent_id] => 0
)
)
[_320_] => Array
(
[_321_] => Array
(
[id] => _321_
[parent_id] => _320_
)
[_325_] => Array
(
[id] => _325_
[parent_id] => _320_
)
)
[_321_] => Array
(
[_322_] => Array
(
[id] => _322_
[parent_id] => _321_
)
[_323_] => Array
(
[_324_] => Array
(
[id] => _324_
[parent_id] => _323_
)
)
)
2. Next, assemble the tree:
function buildTree( $tree, &$lists) {
foreach ($tree as $k => $v) {
// If we have any children for this node, link them in:
if (isset($lists[$k])) {
$tree[$k]['children'] = $lists[$k];
unset($lists[$k]);
// Then go in and find any of that node's children and link them in:
$tree[$k] = buildTree($tree[$k], $lists);
}
}
return $tree;
}
$tree = buildTree($lists[0], $lists);
I think that should make the structure you're looking for, with one
pass through the original list, and one depth-first traversal of the
tree.
Thanks,
Mac
--
Mac Newbold
[email protected]
801-694-6334
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