yii\mongodb\Query::one PHP Method

    public function one($db = null)
    {
        $cursor = $this->buildCursor($db);
        return $this->fetchRows($cursor, false);
    }

 public function actionCheck_login()
 {
     $username = $_POST['username'];
     $pwd = $_POST['pwd'];
     $query = new Query();
     $query->select(['name', 'status', 'password'])->from('admin')->where(['name' => $username]);
     $arr = $query->one();
     if ($arr) {
         if ($arr['password'] == md5($pwd)) {
             $_SESSION['user_id'] = $arr['_id'];
             $_SESSION['user_name'] = $arr['name'];
             if ($arr['name'] != "admin") {
                 $userid = $arr['_id'];
                 //根据用户id查找用户的角色ID
                 $query->select(['role_id'])->from('user_role')->where(['user_id' => "{$userid}"]);
                 $res = $query->one();
                 $role_id = $res['role_id'];
                 //根据角色ID查询所有权限ID,将其ID存入字符串中
                 $q = new Query();
                 $q->select(['node_id'])->from('role_node')->where(['role_id' => $role_id]);
                 $ar = $q->all();
                 $que = new Query();
                 foreach ($ar as $key => $v) {
                     // $node[$key] = $v['node_id'];
                     $idd = $v['node_id'];
                     $que->select(['n_name', 'nickname', 'n_level', 'p_id'])->from('node')->where(['_id' => "{$idd}"])->andwhere(['n_level' => "1"]);
                     $quan[$key] = $que->all();
                 }
                 $yi_quan = array_filter($quan);
                 $_SESSION['yi_quan'] = $yi_quan;
                 $quee = new Query();
                 foreach ($ar as $kk => $vv) {
                     // $node[$key] = $v['node_id'];
                     $iddd = $vv['node_id'];
                     $quee->select(['n_name', 'nickname', 'n_level', 'p_id'])->from('node')->where(['_id' => "{$iddd}"])->andwhere(['n_level' => "2"]);
                     $quanx[$kk] = $quee->all();
                 }
                 $er_quan = array_filter($quanx);
                 $_SESSION['er_quan'] = $er_quan;
             } else {
                 $que = new Query();
                 $que->select(['n_name', 'nickname', 'n_level', 'p_id'])->from('node')->where(['n_level' => "1"]);
                 $yi_quan = $que->all();
                 $_SESSION['yi_q'] = $yi_quan;
                 $quee = new Query();
                 $quee->select(['n_name', 'nickname', 'n_level', 'p_id'])->from('node')->where(['n_level' => "2"]);
                 $er_quan = $quee->all();
                 $_SESSION['er_q'] = $er_quan;
             }
             echo "<script>location.href='index.php?r=site/index'</script>";
         } else {
             echo "<script>alert('密码错误');location.href='index.php?r=public/login'</script>";
         }
     } else {
         echo "<script>alert('用户名或密码错误');location.href='index.php?r=public/login'</script>";
     }
 }