PHP indexed array to nested associative array - php

Question

I need to convert simple array to nested array according to specific rules. I've achived it but I'm looking for better solution.
SIMPLE:
array(4) {
[0]=>
array(2) {
["id"]=>
string(2) "11"
["type"]=>
int(3)
}
[1]=>
array(2) {
["id"]=>
string(2) "10"
["type"]=>
int(2)
}
[2]=>
array(2) {
["id"]=>
string(1) "1"
["type"]=>
int(1)
}
[3]=>
array(2) {
["id"]=>
string(1) "0"
["type"]=>
int(1)
}
}
EXPECTED EFFECT:
array(1) {
[0]=>
array(2) {
["type"]=>
int(1)
["child"]=>
array(1) {
[1]=>
array(2) {
["type"]=>
int(1)
["child"]=>
array(1) {
[10]=>
array(2) {
["type"]=>
int(2)
["child"]=>
array(1) {
[11]=>
array(2) {
["type"]=>
int(3)
["child"]=>
array(0) {
}
}
}
}
}
}
}
}
}
MY SOLUTION (not very satisfying):
$nestedArray = [];
foreach ($simpleArray as $item)
{
if (!empty($nestedArray))
{
$array = $nestedArray;
reset($array);
$firstKey = key($array);
}
$nestedArray[$item['id']]['child'] = $nestedArray;
$nestedArray[$item['id']]['type'] = $item['type'];
if (!empty($firstKey))
{
unset($nestedArray[$firstKey]);
}
}
As I said, I'm looking for more elegant way to achieve that. Rule are very simply: every next item is child of previous.

Answer 1

You could use recursion:
function nest($arr) {
return count($arr) ? ["type" => array_pop($arr)["type"], "child" => nest($arr)] : [];
}
With your example input, it would look like this:
$simpleArray = [
["id" => "11", "type" => 3],
["id" => "10", "type" => 2],
["id" => "1", "type" => 1],
["id" => "0", "type" => 1]
];
function nest($arr) {
return count($arr) ? ["type" => array_pop($arr)["type"], "child" => nest($arr)] : [];
}
$nested = nest($simpleArray));
$nested will have the following value:
[
"type" => 1,
"child" => [
"type" => 1,
"child" => [
"type" => 2,
"child" => [
"type" => 3,
"child" => []
]
]
]
]