Nesting an array based on parent IDs - php

Question

I've been stuck trying to figure this out for a week now. I have an array in the following format:
[
1 => [
'name' => 'Maths',
'parent_category_id' => NULL
],
2 => [
'name' => 'Algebra',
'parent_category_id' => 1
],
3 => [
'name' => 'Expanding brackets',
'parent_category_id' => 2
],
4 => [
'name' => 'Factorising brackets',
'parent_category_id' => 2
],
5 => [
'name' => 'English',
'parent_category_id' => NULL
],
6 => [
'name' => 'Shakespeare',
'parent_category_id' => 5
]
]
and I want to transform it into an array in this format:
[
'Maths' => [
'category_id' => 1,
'questions' => [], //This array will then be filled with questions regarding each of the categories
'children_categories' => [
'Algebra' => [
'category_id' => 2,
'questions' => [],
'children_categories' => [
'Expanding brackets' => [
'category_id' => 3,
'questions' => [],
'children_categories' => []
],
'Factorising brackets' => [
'category_id' => 4,
'questions' => [],
'children_categories' => []
]
]
]
]
],
'English' => [
'category_id' => 5,
'questions' => [],
'children_categories' => [
'Shakespeare' => [
'category_id' => 6,
'questions' => [],
'children_categories' => []
]
]
]
]
So far I've been able to format categories that have no parents, but I for the life of me cannot figure out how to insert a category that has a parent into that parent's children_categories[] array. Here's the code I'm using, I need help figuring out what I should put in the "else" part of the foreach()
foreach($ids_as_keys as $category_id => $info){ //$info contains the name of the category, and the parent's ID (NULL if there is no parent)
if(is_null($info['parent_category_id'])){ //There is no parent, so put it at the root of $nested
$nested[$info['name']] = [
'category_id' => $category_id,
'questions' => [],
'children_categories' => []
];
}else{ //There is a parent, so search through all items (including sub-arrays, sub-sub-arrays etc.) until we find a match for the parent_category_id, and then add it into the children_categories[] array
}
}
return $nested;

Answer 1

I tested this, absolutely works :
$arr = array(
1 => array(
'name' => 'Maths',
'parent_category_id' => NULL
),
2 => array(
'name' => 'Algebra',
'parent_category_id' => 1
),
3 => array(
'name' => 'Expanding brackets',
'parent_category_id' => 2
),
4 => array(
'name' => 'Factorising brackets',
'parent_category_id' => 2
),
5 => array(
'name' => 'English',
'parent_category_id' => NULL
),
6 => array(
'name' => 'Shakespeare',
'parent_category_id' => 5
)
);
foreach ($arr as $key => &$value) {
if ($value['parent_category_id']) {
$arr[$value['parent_category_id']]['children_categories'][] = &$value;
}
else{
$parents[]=$key;
}
}
$result = array();
foreach ($parents as $val) {
$result[$val] = $arr[$val];
}
print_r($result);

Answer 2

This answer is too close may helpful for you
<?php
$array = [
1 => [
'name' => 'Maths',
'parent_category_id' => NULL
],
2 => [
'name' => 'Algebra',
'parent_category_id' => 1
],
3 => [
'name' => 'Expanding brackets',
'parent_category_id' => 2
],
4 => [
'name' => 'Factorising brackets',
'parent_category_id' => 2
],
5 => [
'name' => 'English',
'parent_category_id' => NULL
],
6 => [
'name' => 'Shakespeare',
'parent_category_id' => 5
]
];
//data array
$data = array();
$i = 0;
//gothrough one by one
foreach($array as $key=>$value)
{
//set the parent array
if(is_null($value['parent_category_id']))
{
$data[$value['name']]= array();
$data[$value['name']]['category_id'] = $key;
$data[$value['name']]['questions'] = array();
$data[$value['name']]['children_categories'] = array();
//add the childrens according to the parent
}elseif(array_key_exists($value['parent_category_id'], $array)){
//find the parent
$parent = $array[$value['parent_category_id']];
$data[$parent['name']]['children_categories'][$value['name']] = array();
$data[$parent['name']]['children_categories'][$value['name']]['category_id'] = $key;
$data[$parent['name']]['children_categories'][$value['name']]['questions'] = array();
}
}
//display the result
print_r($data);

Answer 3

Try using recursive function.
function insert_child($curArr,$childArray,&$parentArray){
foreach($parentArray as $key=>&$val){
if(is_array($val) && sizeof($val) > 0 ){
if($val['category_id']==$curArr['parent_category_id']){
$val['children_categories'][$curArr['name']] = $childArray;
return TRUE;
}else{
insert_child($curArr,$childArray,$val['children_categories']);
}
}
}
return FALSE;
}
Where $nest is your input array
$nest = array(
1=>array(
'name' => 'Maths',
'parent_category_id' => NULL
),
2=>array(
'name' => 'Algebra',
'parent_category_id' => 1
),
3=>array(
'name' => 'Expanding brackets',
'parent_category_id' => 2
),
4=>array(
'name' => 'Factorising brackets',
'parent_category_id' => 2
),
5=>array(
'name' => 'English',
'parent_category_id' => NULL
),
6=>array(
'name' => 'Shakespeare',
'parent_category_id' => 5
),
);
code
$result=array();
foreach($nest as $key=>$val){
$temp = array(
'category_id'=>$key,
'questions'=>array(),
'children_categories'=>array(),
);
if(!in_array($val['name'],$result) && $val['parent_category_id']==NULL){
$result[$val['name']] = $temp;
}else{
insert_child($val,$temp,$result);
}
}
echo "<pre>";
print_r($result);
exit();
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