PHP动态多维数组或对象

我正在尝试创建一个递归函数（或方法），在数组变量或对象中存储子层导航 . 这是我有的：

class Navigation extends Database
{

    function build($parent_id = 0)
    {
        $query = 'SELECT id, name, href, parent_id 
        FROM navigation
        WHERE parent_id = '.$parent_id.' 
        ORDER BY name';
        $results = $db->query($query);
        while ($row = $results->fetch_object()) {
            $nav[$row->id] = $row;
            // echo $row;
            $this->build($row->id);
        }
        return $nav;
    }
}

如果你注释 echo $row 一切正常 . 所以我想要它在三层导航中做的是这样的：

Array
(
    [1] => stdClass Object
    (
        [id] => 1
        [name] => Home
        [href] => home.php
        [parent_id] => 0
    )
    [2] => stdClass Object
    (
        [id] => 2
        [name] => Company
        [href] => company.php
        [parent_id] => 0
    )
        [4] => stdClass Object
        (
            [id] => 4
            [name] => Company Vision
            [href] => company_vision.php
            [parent_id] => 2
        )
        [5] => stdClass Object
        (
            [id] => 5
            [name] => Company Goals
            [href] => company_goals.php
            [parent_id] => 2
        )
    [3] => stdClass Object
    (
        [id] => 3
        [name] => Products
        [href] => products.php
        [parent_id] => 0
    )
        [6] => stdClass Object
        (
            [id] => 6
            [name] => Products Shoes
            [href] => products_shoes.php
            [parent_id] => 3
        )
            [7] => stdClass Object
            (
                [id] => 7
                [name] => Nike
                [href] => products_shoes_nike.php
                [parent_id] => 6
            )

)

就像一个例子，所以数组会动态地执行此操作：

$nav[$row->id] = $row; // Home
$nav[$row->id] = $row; // Company
$nav[2][$row->id] = $row; // Company Vision
$nav[2][$row->id] = $row; // Company Goals
$nav[$row->id] = $row; // Products
$nav[3][$row->id] = $row; // Products Shoes
$nav[3][6][$row->id] = $row; // Products Shoes Nike

提前致谢 .

问题：如何创建递归函数/方法并将递归信息存储在变量中而不是回显结果？

问题：（a）PHP每次递归调用时都会覆盖变量（b）解决方案是动态创建一个数组，但我不知道这是否可能