Sort multidimensional array recursive by specific key - php

Question

I'm trying to sort this array recursively by its label:
Array
(
[0] => Array
(
[id] => 6
[label] => Bontakt
[children] => Array
(
)
)
[1] => Array
(
[id] => 7
[label] => Ampressum
[children] => Array
(
[0] => Array
(
[id] => 5
[children] => Array
(
)
[label] => Bome
)
[1] => Array
(
[id] => 8
[children] => Array
(
)
[label] => Aome
)
[2] => Array
(
[id] => 10
[children] => Array
(
)
[label] => Come
)
)
)
[2] => Array
(
[id] => 9
[label] => Contakt
[children] => Array
(
)
)
[3] => Array
(
[id] => 11
[label] => Dead
[children] => Array
(
)
)
)
I've read several Questions, and I feel to be pretty close, but I can't figure out what's not working:
function sortByAlpha($a, $b)
{
return strcmp(strtolower($a['label']), strtolower($b['label'])) > 0;
}
function alphaSort(&$a)
{
foreach ($a as $oneJsonSite)
{
if (count($oneJsonSite["children"]) > 0) alphaSort($oneJsonSite["children"]);
}
usort($a, 'sortByAlpha');
}
alphaSort($jsonSites);
Current output is like this:
Ampressum
Bome
Aome
Come
Bontakt
Contakt
Dead
The children elements are not sorted...

Answer 1

Check this out:
In order to be able to directly modify array elements within the loop precede $value with &. In that case the value will be assigned by reference.
(Picked from here: http://php.net/manual/en/control-structures.foreach.php)
You should try it with this one:
function alphaSort(&$a)
{
foreach ($a as &$oneJsonSite)
{
if (count($oneJsonSite["children"]) > 0) alphaSort($oneJsonSite["children"]);
}
usort($a, 'sortByAlpha');
}