Find latest children in nested categories php - php

Question

I tried to parse a JSON using PHP from url. I need a list of item that have no children - means children field should be empty array and parent_id shouldn't be 0 - means not be parents.
JSON:
{
"body": {
"data": [
{
"id": 1,
"name": "car",
"parent_id": "0",
"children": [
{
"id": 2,
"name": "bmw",
"parent_id": "1",
"children": [
{
"id": 4,
"name": "bmw i8",
"parent_id": "2",
"children": []
}
]
},
{
"id": 3,
"name": "mustang",
"parent_id": "1",
"children": []
}
]
},
{
"id": 5,
"name": "clothes",
"parent_id": "0",
"children": []
},
{
"id": 6,
"name": "mobile",
"parent_id": "0",
"children": [
{
"id": 7,
"name": "apple",
"parent_id": "6",
"children": [
{
"id": 9,
"name": "Iphone 12 pro",
"parent_id": "7",
"children": []
},
{
"id": 10,
"name": "Iphone 11",
"parent_id": "7",
"children": []
}
]
},
{
"id": 8,
"name": "Xiaomi",
"parent_id": "6",
"children": []
}
]
}
]
}
}
Output Expected:
[4,3,9,10,8]
This is my php code that i tried and doesn't work.
$CategoryUrl = file_get_contents(self::CATEGORY_URL,true);
$array = json_decode($CategoryUrl,true);
$list = array();
foreach( $array['body']['data'] as $value ){
if (($value['parent_id'] != 0) && empty($value['children'])) {
foreach( $value['children'] as $val ){
$list[] = $val;
}
}
}
print_r($list);

Answer 1

It is indeed a little tricky to keep track of parent ID values and children call using array_walk_recursive as it jumps directly to its children. However, this can be still accomplished with your own recursive version like below. Keep checking with parent_id and children count. If both constraints satisfy, add them to $result, else keep calling children recursively.
<?php
$str = '{"body":{"data":[{"id":1,"name":"car","parent_id":"0","children":[{"id":2,"name":"bmw","parent_id":"1","children":[{"id":4,"name":"bmw i8","parent_id":"2","children":[]}]},{"id":3,"name":"mustang","parent_id":"1","children":[]}]},{"id":5,"name":"clothes","parent_id":"0","children":[]},{"id":6,"name":"mobile","parent_id":"0","children":[{"id":7,"name":"apple","parent_id":"6","children":[{"id":9,"name":"Iphone 12 pro","parent_id":"7","children":[]},{"id":10,"name":"Iphone 11","parent_id":"7","children":[]}]},{"id":8,"name":"Xiaomi","parent_id":"6","children":[]}]}]}}';
$data = json_decode($str,true);
$result = [];
function walkRecursive($data,&$result){
foreach($data as $entry){
if($entry['parent_id'] != 0 && count($entry['children']) == 0){
$result[] = $entry['id'];
}else{
walkRecursive($entry['children'],$result);
}
}
}
walkRecursive($data['body']['data'],$result);
print_r($result);

Answer 2

We can solve this problem by function call recursive algorithm,
hope it clear for you
$CategoryUrl = file_get_contents(self::CATEGORY_URL,true);
$array = json_decode($CategoryUrl, true);
$items = $array['body']['data'];
$list = [];
findParentIds(items, $list);
// doSomething
print_r($list);
/**
* passe by ref (list)
* #param array $children
* #param $list
*/
function findParentIds(array $children, & $list)
{
foreach ($children as $child) {
// use case 1: has no children and parent_id is 0 , just continue
if (empty($child['children']) && $child['parent_id'] == "0") {
continue;
}
// use case 2: has no children and parent_id is 0 , it's parent item
if (empty($child['children']) && $child['parent_id'] != "0") {
array_push($list, $child['id']);
}
// has children and parent_id is not 0 , recall function to treat use case 1 and 2 ..
findParentIds($child['children'], $list);
}
}