php | Bug with recursion - php

Question

I have a problem with my recursional function. May be you can help me.
My function below:
function showTree($items, $level = 0) {
$arr = [];
foreach ($items as $item) {
$arr[] = str_repeat(":", $level * 2) . $item['name'] . "<br />";
if (!empty($item['children'][0])) {
$level++;
$arr[] = $this->showTree($item['children'], $level);
}
}
return $arr;
}
And this generate the output:
Array
(
[0] => Category1
[1] => Array
(
[0] => ::SubCategory2
[1] => ::SubCategory1
[2] => Array
(
[0] => ::::SubSubCategory
)
)
)
But I need a little bit other data as my output:
Array
(
[0] => Category1
[1] => ::SubCategory2
[2] => ::SubCategory1
[3] => ::::SubSubCategory
)
Where is my mistake? Thanks!
P>S:
Input:
Array
(
[0] => Array
(
[id] => 1
[name] => Category1
[parent] => 0
[children] => Array
(
[0] => Array
(
[id] => 4
[name] => SubCategory2
[parent] => 1
[children] => Array
(
)
)
[1] => Array
(
[id] => 2
[name] => SubCategory1
[parent] => 1
[children] => Array
(
[0] => Array
(
[id] => 3
[name] => SubSubCategory
[parent] => 2
[children] => Array
(
)
)
)
)
)
)
)

Answer 1

Change this line:
$arr[] = $this->showTree($item['children'], $level);
to:
$arr = array_merge($arr, $this->showTree($item['children'], $level));
I.e. don't add the array returned while walking the children as a new value into the current array but append the values from it to the current array.

Answer 2

Try this:
function showTree($items, $level = 0, &$arr = array()) {
foreach ($items as $item) {
$arr[] = str_repeat(":", $level * 2) . $item['name'] . "<br />";
if (!empty($item['children'][0])) {
$level++;
$this->showTree($item['children'], $level, $arr);
}
}
return $arr;
}