无法使JSON多级PHP

Question

在快速应用程序中创建JSON文件时遇到问题

这是我的数据库的样子

    ID  | PICName   | PicPath       |DeviceName
 ---------------------------------------------------
    1   | NewPIC    | new.jpg       |ibrahiem
    2   | NewPIC    | new.jpg       |ibrahiem
    3   | NewPIC    | new.jpg       |ibrahiem
    4   | NewPIC    | new.jpg       |Ali
    5   | NewPIC    | new.jpg       |Ali
    6   | NewPIC    | new.jpg       |Ali

我需要3个级别的JSON

DeviceName ---> ID ---->（PICName，PicPath）

我只是现在如何制作简单的JSON，所以如果我在一些逗号或方括号中有误，请更正我

这是我的简单代码

<?php

$con=mysqli_connect("127.0.0.1","erterte","534234","u13");
if (mysqli_connect_errno()) {
   echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

$return_arr = array();
$return_arr['xx']= array();
$query = "select * from Products order by deviceid";
$result = mysqli_query($con,$query);
$rows = array();

while($r = mysqli_fetch_array($result)) {
    $rows['ID'] = $r['ID'];
    $rows['PicPath'] = $r['PicPath'];
    $rows['DeviceName'] = $r['DeviceName'];
    $rows['PICName'] = $r['PICName'];

    array_push($return_arr['xx'],$rows);

}

echo json_encode($return_arr);
mysqli_close($con);
?>