Thinkphp5实现接口嵌套

$list =  Db::table('pet_info')->select();
        //查询图片
    //   return json_encode($list);
      for($i = 0;$i< count($list);$i++){
            $pid = $list[$i]['id'];
            $list[$i]['imgsrc']=Db::table('upload_img')->where("uoload_pet_id",$pid)->select();
        }
        $this->assign('list',$list);
    //   return json_encode($list);
        return $this->fetch();

[{
  "id": 1,
  "pet_name": "Ceshi ",
  "pet_src1": "",
  "pet_src2": "",
  "pet_src3": "",
  "kinds": 0,
  "pet_sex": 0,
  "pet_age": 0,
  "pet_health": 0,
  "pet_breed": "",
  "pet_desc": "",
  "pet_publi": "15368666279",
  "pub_name": "\u547c\u547c\u547c",
  "pub_address": "\u54c8\u54c8\u54c8",
  "pub_phone": "11111111111",
  "imgsrc": [
  {
      "id": 1,
      "src": "xxxxx.png "
  },
  {
      "id": 2,
      "src": "xxxxx.png "
  }
  ]
}]