Recursive loop for category - php

Question

I'm trying to implement a category system on my website. The problem is that a category can have child.
So far, my table category looks like that :
id, name, parent_id
So far, I made a loop, but it only works for 2 levels. Here is my code :
for($i=0;$i<count($data);$i++){
$tree[$data[$i]->name] = array();
for($j=0;$j<count($data);$j++){
if($data[$j]->parent_id == $data[$i]->id){
$tree[$data[$i]->name][] = $data[$j]->name;
}
}
}
It return me an array as it :
Array
(
[0] => Array
(
[1] => Cat1
[children] => Array
(
[12] => sub cat 1
[13] => sub cat 2
[14] => sub cat 3
)
)
[1] => Array
(
[2] => Cat2
)
[2] => Array
(
[3] => Cat3
)
)
How can I make it efficient and recursive to have something more like :
Array
(
[0] => Array
(
[1] => Cat1
[children] => Array
(
[12] => sub cat 1
[13] => sub cat 2
[14] => sub cat 3
[children] => Array
(
[1] => sub sub cat 1
)
)
)
[1] => Array
(
[2] => Cat2
)
[2] => Array
(
[3] => Cat3
)
)
Thanks for your help
EDIT
I'm working on Zend, and it return me the data as it :
Zend_Db_Table_Rowset Object
(
[_data:protected] => Array
(
[0] => Array
(
[id] => 1
[name] => Cinema
[type] => category
[slug] => cinema
[parent_id] => -1
)
[1] => Array
(
[id] => 2
[name] => Horror
[type] => category
[slug] => horror
[parent_id] => 1
)

Answer 1

If you want to apply this type of structure best to use child in other table with parent id as a foreign key.
so with that u can have recursive category posting.
so the table structure will be like this
ch_id, parent_id, child

Answer 2

You should check out Nested Sets, a methodology to store and retrieve date trees in/out of relational databases (what in fact your categories are). For this, you have to adapt your database scheme a little bit (as described in the link or in the several tutorials about nested sets). For PHP, there are several libraries providing Nested Set capabilities, for instance this list.

Answer 3

This should help you out.
It Iterates over every member of the array and checks it's position in the tree structure per level and dependency.
function get_children($data, $parent_id = false) {
$result = array();
foreach ($data as $i => $content) {
if ($parent_id != false && $content['id'] != $parent_id) # other levels
continue;
if ($parent_id === false && !empty($content['parent_id'])) # top level
continue;
$leaf = array(
'id' => $content['id'],
'parent_id' => $content['parent_id'],
'name' => $conten['name']
);
$leaf['children'] = get_children($data, $leaf['id']);
$result[$leaf['id']] = $leaf;
}
return $result;
}
$result = get_children($data);
print_r($result);
Edit: bug fixes