Assign parent ids to children of multidimensional arrays - php

Question

I need to assign parent ids to all the children of a multidimensional array in PHP.
Array
(
[expanded] => 1
[key] => root_1
[title] => root
[children] => Array
(
[0] => Array
(
[folder] => 1
[key] => 34
[title] => YAY PROJECTS
)
[1] => Array
(
[expanded] => 1
[folder] => 1
[key] => 6
[title] => Grand Designs Episodes
[children] => Array
(
[0] => Array
(
[folder] => 1
[key] => 8
[title] => AU Episodes
)
[1] => Array
(
[expanded] => 1
[folder] => 1
[key] => 7
[title] => UK Episodes
[children] => Array
(
[0] => Array
(
[folder] =>
[key] => 9
[title] => Start something
)
[1] => Array
(
[folder] =>
[key] => 2
[title] => Grand Designs Season 10
)
)
)
)
)
[2] => Array
(
[expanded] => 1
[folder] => 1
[key] => 5
[title] => Animations
[children] => Array
(
[0] => Array
(
[folder] =>
[key] => 4
[title] => Futurama Episode 191
)
[1] => Array
(
[folder] =>
[key] => 3
[title] => Miniscule Series 5 Ep 1
)
[2] => Array
(
[folder] =>
[key] => 1
[title] => The Simpsons Episode 459
)
)
)
[3] => Array
(
[folder] => 1
[key] => 11
[title] => Test Folder
)
[4] => Array
(
[folder] => 1
[key] => 10
[title] => Testing
)
)
)
At first I thought this would be fairly trivial, however my solution quickly falls apart assigning the wrong parent_ids.
public function generateParentIds(array $input, $parentId = 0)
{
$return = [];
foreach ($input as $key => $value) {
if (is_array($value)) {
$value = $this->generateParentIds($value, $parentId);
if (isset($value['children'])) {
$parentId = $value['key'];
}
if (!is_int($key)) {
$return['parent_id'] = $parentId;
}
}
$return[$key] = $value;
}
return $return;
}
I'm not sure whats going on, I did a lot of research but couldn't find any examples, so I'd be very grateful for some help.

Answer 1

Assuming that each child should get the immediate parent's key value as its parent_id, this should do what you want. Note that it modifies the array in place ($input is passed by reference to the function, and the foreach loop uses a reference to $child), rather than attempting to merge returned values.
function generateParentIds(&$input, $parentId = 0) {
$input['parent_id'] = $parentId;
if (isset($input['children'])) {
foreach ($input['children'] as &$child) {
generateParentIds($child, $input['key']);
}
}
}
generateParentIds($input);
Output is too long to show here but there's a demo at 3v4l.org