PHP function returning array index path - php

Question

I've been trying to write a PHP function which searches the id index valeus in array, and once found, returns the path which lead to it's discovery.
Take the following array:
Array
(
[0] => Array
(
[id] => 1
[data] => Array
(
[0] => Array
(
[id] => 8
)
[1] => Array
(
[id] => 9
)
[2] => Array
(
[id] => 10
[data] => Array
(
[0] => Array
(
[id] => 15
[data] => Array
(
[0] => Array
(
[id] => 22
)
)
)
[1] => Array
(
[id] => 21
)
)
)
)
)
)
If looking for [id] => 21 it would return array(1,10). However, in numerous attempts I have failed. The set path should be set to the index id. However, I cannot figure it out. Any words of guidance are much appreciated.

Answer 1

This functions returns array(1,10) for OP example
(will leave that other answer just in case someone will look for normal "path searching")
function search_data($needle, $haystack) {
if (is_array($haystack)) {
foreach($haystack as $data) {
if ($data['id'] == $needle) return array();
if (isset($data['data'])) {
if (($path = search_data($needle, $data['data'])) !== false) return array_merge(array($data['id']), $path);
}
}
}
return false;
}

Answer 2

This functions returns array(0,'data',2,'data',1,'id') for OP example (i.e. full path to value)
Function which searches for $key => $value pair in array and returns the path:
function array_search_r($key, $value, $haystack, $strict = null) {
$strict = $strict ?: false;
if (is_array($haystack)) {
foreach($haystack as $k => $v) {
if ($strict ? ($k === $key && $v === $value) : ($k == $key && $v == $value)) return array($k);
if(($path = array_search_r($key, $value, $v, $strict)) !== false) return array_merge(array($k), $path);
}
}
return false;
}