Get all children items from flat array with nested data structure - php

Question

I have a flat array of categories. All categories have ID, Parent_id and Name.
The root categories have Parent_id equal to null. They have subcategories that might have them as their parents and their might be subsubcategories that have subcategories as parents. (their might be a lot of levels).
I can get all categories with a single query into a flat array. What I need is - If I take a category (or a subcaegory), how can I get a list of all nested categories (subcategories, subsubcategories) that are included in this category? Got stack with that problem :(
Array looks like this:
Array
(
[0] => Array
(
[pk_i_id] => 2
[fk_i_parent_id] =>
[i_expiration_days] => 30
[i_position] => 0
[b_enabled] => 1
[b_price_enabled] => 1
[s_icon] =>
)
[1] => Array
(
[pk_i_id] => 4
[fk_i_parent_id] =>
[i_expiration_days] => 30
[i_position] => 6
[b_enabled] => 1
[b_price_enabled] => 1
[s_icon] =>
)
[2] => Array
(
[pk_i_id] => 12
[fk_i_parent_id] =>
[i_expiration_days] => 60
[i_position] => 11
[b_enabled] => 1
[b_price_enabled] => 1
[s_icon] =>
)
[3] => Array
(
[pk_i_id] => 13
[fk_i_parent_id] => 108
[i_expiration_days] => 30
[i_position] => 0
[b_enabled] => 1
[b_price_enabled] => 1
[s_icon] =>
)

Answer 1

You can use recursion. It will be looks like this:
function outTree(array $tree, $parentId = null) {
echo '<ul>';
foreach ($tree as $row) {
if ($row['fk_i_parent_id'] == $parent_id) {
echo '<li>' . $row['pk_i_id'];
echo outTree($tree, $row['pk_i_id']);
echo '</li>';
}
}
echo '</ul>';
}