PHP Branching Recursion With Repeating Children - php

Question

I have a flat structure that I need to convert to a nested tree-like structure. This is different from other Stack Overflow questions because the children can repeat (i.e. can have the same questionId and parentId). I have attempted to solve this with branching recursion with no luck.
Input (flat array):
[
[
'questionId' => 1,
'name' => 'albumName',
'parentId' => 0,
'answer' => "Name of album",
],
[
'questionId' => 2,
'name' => 'albumGenre',
'parentId' => 0,
'answer' => "album genre",
],
[
'questionId' => 3,
'name' => 'trackStart',
'parentId' => 0,
],
[
'questionId' => 4,
'name' => 'trackName',
'parentId' => 3,
'answer' => "Track One",
],
[
'questionId' => 5,
'name' => 'trackEnd',
'parentId' => 3,
],
[
'questionId' => 3,
'name' => 'trackStart',
'parentId' => 0,
],
[
'questionId' => 4,
'name' => 'trackName',
'parentId' => 3,
'answer' => "Track Two",
],
[
'questionId' => 6,
'name' => 'artistStart',
'parentId' => 3,
],
[
'questionId' => 7,
'name' => 'artistName',
'parentId' => 6,
'answer' => "Artist Name",
],
[
'questionId' => 8,
'name' => 'artistEnd',
'parentId' => 6,
],
[
'questionId' => 5,
'name' => 'trackEnd',
'parentId' => 3,
],
[
'questionId' => 9,
'name' => 'albumDate',
'parentId' => 0,
'answer' => "album Date",
]
]
Desired Output (nested array):
[
'albumName' => 'Album Name',
'albumGenre' => 'Album Genre',
'trackStart' => [
[
'trackName' => 'Track One'
],
[
'trackName' => 'Track Two',
'artistStart' => [
[
'artistName' => 'Artist Name'
]
]
]
],
'albumDate' => 'album Date'
]

Answer 1

You can solve this using Reference Pointers:
$newArray = array();
$pointer[] = &$newArray;
foreach($arr as $ar) {
if(stristr($ar['name'], "start")) { // Start
$pointer[] = &$pointer[count($pointer)-1][$ar['name']][];
} else if(stristr($ar['name'], "end")) { // End
array_pop($pointer);
} else {
$pointer[count($pointer)-1][$ar['name']] = $ar['answer'];
}
}
To make it faster you can use stripos($ar['name'], "start") !== false;