I'm trying to create a list of categories with any number of sub categories, where sub categories can also has their own sub categories.
I have selected all categories from the Mysql db, the cats are in a standard associate array list, each category has an id, name, parentid where the parentid is 0 if it's top level.
I basically want to be able to take the single level array of cats and turn it into a multidimensional array structure where each category can have an element which will contain an array of subcats.
Now, I can easily achieve this by looping a query for each category but this is far from ideal, I'm trying to do it without any extra hits on the db.
I understand I need a recursive function for this. Can anyone point me in the right direction for this tree style structure?
Cheers
This does the job:
$items = array(
(object) array('id' => 42, 'parent_id' => 1),
(object) array('id' => 43, 'parent_id' => 42),
(object) array('id' => 1, 'parent_id' => 0),
);
$childs = array();
foreach($items as $item)
$childs[$item->parent_id][] = $item;
foreach($items as $item) if (isset($childs[$item->id]))
$item->childs = $childs[$item->id];
$tree = $childs[0];
print_r($tree);
This works by first indexing categories by parent_id. Then for each category, we just have to set category->childs
to childs[category->id]
, and the tree is built !
So, now $tree
is the categories tree. It contains an array of items with parent_id=0, which themselves contain an array of their childs, which themselves ...
Output of print_r($tree)
:
stdClass Object
(
[id] => 1
[parent_id] => 0
[childs] => Array
(
[0] => stdClass Object
(
[id] => 42
[parent_id] => 1
[childs] => Array
(
[0] => stdClass Object
(
[id] => 43
[parent_id] => 42
)
)
)
)
)
So here is the final function:
function buildTree($items) {
$childs = array();
foreach($items as $item)
$childs[$item->parent_id][] = $item;
foreach($items as $item) if (isset($childs[$item->id]))
$item->childs = $childs[$item->id];
return $childs[0];
}
$tree = buildTree($items);
$items = array(
array('id' => 42, 'parent_id' => 1),
array('id' => 43, 'parent_id' => 42),
array('id' => 1, 'parent_id' => 0),
);
$childs = array();
foreach($items as &$item) $childs[$item['parent_id']][] = &$item;
unset($item);
foreach($items as &$item) if (isset($childs[$item['id']]))
$item['childs'] = $childs[$item['id']];
unset($item);
$tree = $childs[0];
So the array version of the final function:
function buildTree($items) {
$childs = array();
foreach($items as &$item) $childs[$item['parent_id']][] = &$item;
unset($item);
foreach($items as &$item) if (isset($childs[$item['id']]))
$item['childs'] = $childs[$item['id']];
return $childs[0];
}
$tree = buildTree($items);