Convert flat PHP array to multidimensional array - php

Question

I have the following array structure:
[parents] => Array
(
[0] => Array
(
[id] => 1
[user_id] => 1
[created] => 2014-11-09 13:47:37
[content] => This is a test discussion
[status] => 1
[parent] => 0
[project_id] => 1
)
[1] => Array
(
[id] => 4
[user_id] => 1
[created] => 2014-11-09 13:52:02
[content] => 456789
[status] => 1
[parent] => 0
[project_id] => 1
)
)
[children] => Array
(
[0] => Array
(
[id] => 2
[user_id] => 1
[created] => 2014-11-09 13:47:53
[content] => This is a test reply....
[status] => 1
[parent] => 1
[project_id] => 1
)
[1] => Array
(
[id] => 3
[user_id] => 1
[created] => 2014-11-09 13:48:13
[content] => This is a test reply....!!!
[status] => 1
[parent] => 1
[project_id] => 1
)
[2] => Array
(
[id] => 5
[user_id] => 1
[created] => 2014-11-09 13:52:17
[content] => 8765432
[status] => 1
[parent] => 4
[project_id] => 1
)
)
I would like to merge them into a parent/child relationship so it looks like follows:
[parents] => Array
(
[0] => Array
(
[id] => 1
[user_id] => 1
[created] => 2014-11-09 13:47:37
[content] => This is a test discussion
[status] => 1
[parent] => 0
[project_id] => 1
[children] => Array
(
[0] => Array
(
[id] => 2
[user_id] => 1
[created] => 2014-11-09 13:47:53
[content] => This is a test reply....
[status] => 1
[parent] => 1
[project_id] => 1
)
[1] => Array
(
[id] => 3
[user_id] => 1
[created] => 2014-11-09 13:48:13
[content] => This is a test reply....!!!
[status] => 1
[parent] => 1
[project_id] => 1
)
)
)
)
How could I go about doing that with PHP?

Answer 1

Assuming that all ids are unique in your parents array, you can do this:
// build a new array using parent's ID values as the key,
// to simplify searching for parent IDs.
foreach ($parents as $key => $value){
$merged[$value['id']] = $value;
}
foreach ($children as $child){
$parentID = $child['parent'];
if (array_key_exists( $parentID, $merged )) {
// add the child array to its parent's ['children'] value
$merged[$parentID]['children'][] = $child;
}
}
In the resulting array $merged, the key of each parent item will be set to its id, and all children will be nested under their corresponding parents.