get parent nodes from a node tree array - php

Question

[
{
"id": 1573695284631,
"name": "Cars",
"pid": 0,
"children": [
{
"id": 1573695292010,
"name": "Audi",
"pid": 1573695284631
},
{
"id": 1573695305619,
"name": "BMW",
"pid": 1573695284631,
"children": [
{
"id": 1573695328137,
"name": "3 Series",
"pid": 1573695305619
},
{
"id": 1573695335102,
"name": "X5",
"pid": 1573695305619
}
]
}
]
},
{
"id": 1573695348647,
"name": "Motorcycles",
"pid": 0,
"children": [
{
"id": 1573695355619,
"name": "Ducatti",
"pid": 1573695348647
}
]
}
]
Suppose I have this node-tree-like array in PHP (represented above in json for readability). For a given child node ID, I would like to find all parent node IDs that it's nested under. For example,
getParentNodes($haystack, $child_node_id=1573695328137); //[1573695284631, 1573695292010, 1573695305619]
I assume this is a use case for recursion. Here's my best attempt:
function getParentNodes($haystack, $child_node_id) {
if( empty($haystack->children) )
return;
foreach($haystack->children as $child) {
if($child->id == $child_node_id) {
// $child found, now recursively get parents
} else {
getParentNodes($child, $child_node_id);
}
}
}

Answer 1

This one will walk the tree until it hits the desired id.
In all cases where the leaf is not the desired one, it will return false - and collapse up the stack resulting in false or an array of parent-ids if the child is found.
Code
function getParentNodes($haystack, $child_node_id) {
foreach ($haystack as $element) {
if ($element['id'] === $child_node_id) {
// return [$element['id']]; // uncomment if you want to include child itself
return [];
} else if (array_key_exists('children', $element)) {
$parentNodes = getParentNodes($element['children'], $child_node_id);
if ($parentNodes !== false) {
return [$element['id'], ...$parentNodes];
}
}
}
return false;
}
Outputs parent ids:
array(2) {
[0]=>
int(1573695284631)
[1]=>
int(1573695305619)
}
Working example.

Answer 2

You missing return result. This is what you want.
function getParentNodes($arr, $child_node_id) {
$result = [];
foreach($arr as $item) {
if($item->pid == $child_node_id) {
$result[] = $item->id;
}
if(!empty($item->children)) {
$result[] = getParentNodes($item->children, $child_node_id);
}
}
return $result;
}
also you need get values as flat array
$values = getParentNodes($values, 1573695284631);
// do flat arr
array_walk_recursive($values,function($v) use (&$result){ $result[] = $v; });
// your values
var_dump($result);
Source reference for flat array

Answer 3

I ended up writing 2 recursive functions
function treeSearch($needle, $haystack) {
foreach($haystack as $node) {
if($node->id == $needle) {
return $node;
} elseif ( isset($node->children) ) {
$result = treeSearch($needle, $node->children);
if ($result !== false){
return $result;
}
}
}
return false;
}
treeSearch will find the node in the tree, then I need to recursively go up the tree until the parent id (pid) is 0
function getParents($node, $hierarchy, $all_parent_ids=[]) {
if($node->pid != 0) {
$parent_node = treeSearch($node->pid, $hierarchy);
$all_parent_ids[] = $parent_node->id;
$result = getParents($parent_node, $hierarchy, $all_parent_ids);
if ($result !== false){
return $result;
}
}
return $all_parent_ids;
}
then, supposing the tree is called $tree I can call them like:
$node = treeSearch(1573695328137, $tree);
$parents = getParents($node, $tree);

Answer 4

This is the best solution to take the parent of a child !
function getPathParent($id, $tree='',$opts='', &$path = array()) {
$in = array_replace(array(
'id'=>'id',
'child'=>'children',
'return'=>'id'
),(array)$opts);
if ( is_array($tree) && !empty($tree) ){
foreach ($tree as $item) {
if ($item[$in['id']] == $id) {
array_push($path, $item[$in['return']]);
return $path;
}
if ( isset($item[$in['child']]) && !empty($item[$in['child']]) ) {
array_push($path, $item[$in['return']]);
if (getPathParent($id, $item[$in['child']],$opts, $path) === false) {
array_pop($path);
} else {
return $path;
}
}
}
}
return false;
}
$tree = [
[
"id" => 1573695284631,
"name" => "Cars",
"pid" => 0,
"children" => [
[
"id" => 1573695292010,
"name" => "Audi",
"pid" => 1573695284631
],
[
"id" => 1573695305619,
"name" => "BMW",
"pid" => 1573695284631,
"children" => [
[
"id" => 1573695328137,
"name" => "3 Series",
"pid" => 1573695305619
],
[
"id" => 1573695335102,
"name" => "X5",
"pid" => 1573695305619
]
]
]
]
],
[
"id" => 1573695348647,
"name" => "Motorcycles",
"pid" => 0,
"children" => [
[
"id" => 1573695355619,
"name" => "Ducatti",
"pid" => 1573695348647
]
]
]
];
$getParentNode = getPathParent(1573695335102,$tree);
var_export($getParentNode);
// return:
/*
array (
0 => 1573695284631,
1 => 1573695305619,
2 => 1573695335102,
)
*/
$getParentNode = getPathParent(1573695335102,$tree,array('return'=>'name'));
var_export($getParentNode);
// return:
/*
array (
0 => 'Cars',
1 => 'BMW',
2 => 'X5',
)
*/
$getParentNode = getPathParent(1573695335102,$tree,array('id'=>'id','child'=>'children','return'=>'pid'));
var_export($getParentNode);
// return:
/*
array (
0 => 0,
1 => 1573695284631,
2 => 1573695305619,
)
*/