Recursive PHP function not returning result - php

Question

Just a simple function to build breadcrumbs based off a simple database table where there are columns:
id, parent, title
The "parent" column can be 0 for top-level, or the "id" of another row for sub-categories (unlimited depth). All I'm trying to do is have a function that'll help me build breadcrumbs from it, starting from the "id" of the bottom-most category I specify and working its way up to the top parent. Here's what I have:
function getCategoryParents($id=0, $out=array()) {
$id = (int)$id;
if ($id > 0) {
$query = "SELECT * FROM `" .$this->tables['categories']. "` WHERE (`id`=" .$id. ")";
$cat = sqlfetch(sqlquery($query));
array_push($out, $cat);
if ($cat['parent']) {
$this->getCategoryParents($cat['parent'], $out);
} else {
return $out;
}
} else {
return $out;
}
}
But it's not returning anything. But, if I do a print_r($out) from within the function instead of return, ex:
if ($cat['parent']) {
$this->getCategoryParents($cat['parent'], $out);
} else {
echo print_r($out);
}
It outputs the array just fine. But I need to be able to actually work with the array, so I need it returned from the function. I'm sure I'm missing something incredibly small, but I cannot figure it out for the life of me!
Also, I don't want to do a global variable, and also need the info of the category id specified in the initial function call as part of the array as well (as I was trying to do).

Answer 1

Following the suggestions, here's what ended up working:
function getCategoryParents($id=0) {
$out = array();
$id = (int)$id;
if ($id > 0) {
$query = "SELECT * FROM `" .$this->tables['categories']. "` WHERE (`id`=" .$id. ")";
$cat = sqlfetch(sqlquery($query));
array_push($out, $cat);
if ($cat['parent']) {
$out = array_merge($out, $this->getCategoryParents($cat['parent']));
}
}
return $out;
}