通过引用递归函数传递数组

Question

我需要递归获取类别名称。我无法将数组传递给递归函数。

function getCat($id, array &$cats) {
    global $db;
    $cc = $db->prepare("SELECT * FROM tbl_articlecategories WHERE id=?");
    $cc->execute(array($id));
    $cat = $cc->fetch(PDO::FETCH_OBJ);
    $cats[] = $cat->title;
    if ($cat->nodeId != 0) { // top node
        getCat($cat->nodeId, $cats);
    } else {
        return implode(' => ', array_reverse($cats));
    }
}

var_dump(getCat(21));

示例数据：

id | title | nodeId
1    Main         0
5    Electronics  1
21   TV's         5