Convert 2d array into 3d with PHP - php

Question

There are simple 2d array with some sort of tree like this:
node1
node2
node3
It's structure is:
array(
array (
'id' : 1,
'pid': 0,
'title' : 'node1',
'level' : 1
),
array (
'id' : 2,
'pid': 1,
'title' : 'node2',
'level' : 2
),
array (
'id' : 3,
'pid': 2,
'title' : 'node3',
'level' : 3
),
)
Is there solutions with PHP to convert this array into:
array(
array (
'id' : 1,
'title' : 'node1',
'child' : array (
'id' : 2,
'title' : 'node2',
'child' : array (
'id' : 3,
'title' : 'node3',
),
),
)
...
)

Answer 1

Found #SO PHP Traversing Function to turn single array into nested array with children - based on parent id
$inArray = array(
array('ID' => '1', 'parentcat_ID' => '0'),
array('ID' => '2', 'parentcat_ID' => '0'),
array('ID' => '6', 'parentcat_ID' => '1'),
array('ID' => '7', 'parentcat_ID' => '1'),
array('ID' => '8', 'parentcat_ID' => '6'),
array('ID' => '9', 'parentcat_ID' => '1'),
array('ID' => '13', 'parentcat_ID' => '7'),
array('ID' => '14', 'parentcat_ID' => '8'),
);
function makeParentChildRelations(&$inArray, &$outArray, $currentParentId = 0) {
if(!is_array($inArray)) {
return;
}
if(!is_array($outArray)) {
return;
}
foreach($inArray as $key => $tuple) {
if($tuple['parentcat_ID'] == $currentParentId) {
$tuple['children'] = array();
makeParentChildRelations($inArray, $tuple['children'], $tuple['ID']);
$outArray[] = $tuple;
}
}
}
$outArray = array();
makeParentChildRelations($inArray, $outArray);
print_r($outArray);

Answer 2

<?php
$p = array(0 => array());
foreach($nodes as $n)
{
$pid = $n['pid'];
$id = $n['id'];
if (!isset($p[$pid]))
$p[$pid] = array('child' => array());
if (isset($p[$id]))
$child = &$p[$id]['child'];
else
$child = array();
$p[$id] = $n;
$p[$id]['child'] = &$child;
unset($p[$id]['pid']);
unset($p[$id]['level']);
unset($child);
$p[$pid]['child'][] = &$p[$id];
// $p[$pid]['child'] = &$p[$id]; // or this, if only one child
}
$nodes = $p['0']['child'];
unset($p);
?>
If each node can only have one child, then replace the one line with $p[$pid]['child'] = &$p[$id];.
(Edit: fixed it to work regardless of how the nodes are sorted.)