在获取的结果中增加一个对象名称

目前获取到的结果是 如示例1 结构 ，
表中没有value字段
$tree = M('Kind')->where(array('status'=>1))->field('id, title as name')->select();
$this->ajaxReturn($tree);
想要获取 如示例2 的结构，有方便的方法吗？
框架是 thinkphp

//示例1
[
  {"id": "4","name": "服饰鞋类箱包"},
  {"id": "8","name": "母婴"}
]

//示例2
[
    {"value":{"id":4,"name":"服饰鞋类箱包" }},
    {"value":{ "id":8,"name":"母婴"}}
]

---

$tree = M('Kind')->where(array('status'=>1))->field('id, title as name')->select();
$return_data = array();
foreach ($tree as $val){
    $return_data[] = array("value" => $val);
}
$this->ajaxReturn($return_data);