PHP - Find parent key of array - php

Question

I'm trying to find a way to return the value of an array's parent key.
For example, from the array below I'd like to find out the parent's key where $array['id'] == "0002".
The parent key is obvious because it's defined here (it would be 'products'), but normally it'd be dynamic, hence the problem. The 'id' and value of 'id' is known though.
[0] => Array
(
[data] =>
[id] => 0000
[name] => Swirl
[categories] => Array
(
[0] => Array
(
[id] => 0001
[name] => Whirl
[products] => Array
(
[0] => Array
(
[id] => 0002
[filename] => 1.jpg
)
[1] => Array
(
[id] => 0003
[filename] => 2.jpg
)
)
)
)
)

Answer 1

A little crude recursion, but it should work:
function find_parent($array, $needle, $parent = null) {
foreach ($array as $key => $value) {
if (is_array($value)) {
$pass = $parent;
if (is_string($key)) {
$pass = $key;
}
$found = find_parent($value, $needle, $pass);
if ($found !== false) {
return $found;
}
} else if ($key === 'id' && $value === $needle) {
return $parent;
}
}
return false;
}
$parentkey = find_parent($array, '0002');

Answer 2

Since you have a tree structure either of a BFS or DFS can do it. Since the structure is variable a recursive solution would work well. Simply return a sentinel when you find the value, then return the key in the caller.

Answer 3

function array_to_xml($array, $rootElement = null, $xml = null) {
$_xml = $xml;
if ($_xml === null) {
$_xml = new SimpleXMLElement($rootElement !== null ? $rootElement : '<root/>');
}
$has_int_key = 0;
foreach ($array as $k => $v) {
if (is_array($v)) {
if(is_int($k)){
$this->array_to_xml($v, $k, $_xml->addChild($rootElement));
}
else {
foreach($v as $key=>$value) {
if(is_int($key)) $has_int_key = 1;
}
if ($has_int_key) {
$this->array_to_xml($v, $k, $_xml);
} else {
$this->array_to_xml($v, $k, $_xml->addChild($k));
}
}
}
else {
$_xml->addChild($k, $v);
}
}
return $_xml->asXML();
}