PHP Adjacency Data to Nested Array - php

Question

I am having array as follows:
Array
(
[0] => Array
(
[question_id] => 1
[question_title] => Q1
[child_question_id] => NULL
)
[1] => Array
(
[question_id] => 2
[question_title] => Q2
[child_question_id] => NULL
)
[2] => Array
(
[question_id] => 3
[question_title] => Q3
[child_question_id] => 4
)
[3] => Array
(
[question_id] => 3
[question_title] => Q3
[child_question_id] => 5
)
[4] => Array
(
[question_id] => 4
[question_title] => Q4
[child_question_id] => NULL
)
[5] => Array
(
[question_id] => 5
[question_title] => Q5
[child_question_id] => NULL
)
[6] => Array
(
[question_id] => 6
[question_title] => Q6
[child_question_id] => NULL
)
[7] => Array
(
[question_id] => 7
[question_title] => Q7
[child_question_id] => 6
)
)
And using PHP I am expecting result as:
Array
(
[0] => Array
(
[question_id] => 1
[question_title] => Q1
[child_question_id] => NULL
)
[1] => Array
(
[question_id] => 2
[question_title] => Q2
[child_question_id] => NULL
)
[2] => Array
(
[question_id] => 3
[question_title] => Q3
[children] => array(
[0] => Array
(
[question_id] => 4
[question_title] => Q4
)
[1] => Array
(
[question_id] => 5
[question_title] => Q5
)
)
)
[3] => Array
(
[question_id] => 7
[question_title] => Q7
[children] => array(
[0] => Array
(
[question_id] => 6
[question_title] => Q6
)
)
)
)
I tried to build final array using following logic:
Traversing array to collect child ids and child data
Traversing array again and match items child id with child array
formed earlier, if found then create children array
Could you please help me out to create better solution?

Answer 1

Did you mean something like that?
$i = 0;
$new = array();
$unsetter = array();
foreach($array as $val)
{
$new[$i] = array();
foreach($val as $key => $data)
{
if(($key == 'child_question_id') && (!is_null($data)))
{
$new[$i]['children'] = array();
$new[$i]['children']['question_id'] = $data;
$new[$i]['children']['question_title'] = $array[$data]['question_title'];
$unsetter[] = $data;
} else {
$new[$i][$key] = $data;
}
}
$i++;
}
foreach($unsetter as $uns)
{
unset($new[$uns]);
}
$new = array_values($new);
var_dump($new);
This will output
array (size=5)
0 =>
array (size=3)
'question_id' => int 1
'question_title' => string 'Q1' (length=2)
'child_question_id' => null
1 =>
array (size=3)
'question_id' => int 2
'question_title' => string 'Q2' (length=2)
'child_question_id' => null
2 =>
array (size=3)
'question_id' => int 3
'question_title' => string 'Q3' (length=2)
'children' =>
array (size=2)
'question_id' => int 4
'question_title' => string 'Q4' (length=2)
3 =>
array (size=3)
'question_id' => int 3
'question_title' => string 'Q3' (length=2)
'children' =>
array (size=2)
'question_id' => int 5
'question_title' => string 'Q5' (length=2)
4 =>
array (size=3)
'question_id' => int 7
'question_title' => string 'Q7' (length=2)
'children' =>
array (size=2)
'question_id' => int 6
'question_title' => string 'Q6' (length=2)
Live Demo