Build Tree Structure from array

gistfile1.txt

   public function getPagesForSpace() {
        $arr = array();
        $result = $this->query("SELECT * FROM pages ORDER BY id ASC");
        if($result !== false) {
            while ($row = $result->fetch_assoc()) {
                $arr[] = $row;
            }
            function buildTree(array $elements, $parentId = 0) {
                $branch = array();

                foreach ($elements as $element) {
                    if($element['sub_for'] == $parentId) {
                        $children = buildTree($elements, $element['id']);
                        if($children) {
                            $element['children'] = $children;
                        }
                        $branch[] = $element;
                    }
                }

                return $branch;
            }

            return $tree = buildTree($arr);
        }
    }

This simple example will crate something like this:
When table structure is
id <-- parent_id

Array
(
    [0] => Array
        (
            [id] => 1
            [title] => Space 1
            [content] => 
            [sub_for] => 0
            [for_space] => 1
            [category] => 0
            [created] => 1453716270
            [created_from] => 1
            [children] => Array
                (
                    [0] => Array
                        (
                            [id] => 2
                            [title] => Sub page 1
                            [content] => 
                            [sub_for] => 1
                            [for_space] => 1
                            [category] => 0
                            [created] => 1453716312
                            [created_from] => 1
                        )

                    [1] => Array
                        (
                            [id] => 3
                            [title] => Sub Page 2
                            [content] => 
                            [sub_for] => 1
                            [for_space] => 1
                            [category] => 0
                            [created] => 1453716322
                            [created_from] => 1
                            [children] => Array
                                (
                                    [0] => Array
                                        (
                                            [id] => 4
                                            [title] => Sub Page 3
                                            [content] => 
                                            [sub_for] => 3
                                            [for_space] => 1
                                            [category] => 0
                                            [created] => 1453716335
                                            [created_from] => 1
                                        )

                                )

                        )

                )

        )

    [1] => Array
        (
            [id] => 5
            [title] => Space 2
            [content] => 
            [sub_for] => 0
            [for_space] => 1
            [category] => 0
            [created] => 1453716354
            [created_from] => 1
        )

)
``