php插入数组在特定位置的其他数组？

I want to insert the detail array in the data array under specific areas.

For instance, the value of the bdh key in the detail array should be placed in the bdh key of the data array, replacing the empty array that is there to begin with. Similarly, the value of the hadoop key in the detail array should replace the empty array that the hadoop key in the data array currently has. This replacement should happen for every key in the details array.

How do I accomplish this?

Data array

{"data":
    {
        "categories":
        {
            "articles":
            {
                "bdh":[],
                "hadoop":[]
            },
            "videos":
            {
                "bdh Videos":[],
                "hadoop Videos":[]
            }   
        }
    }
}

Detail array

{"details":{
    "bdh":
        [
            {"id":1, "name":"bdh article 1", "body":"this is bdh article 1 body."},
            {"id":2, "name":"bdh article 2", "body":"this is bdh article 2 body."}
        ],
    "hadoop":
        [
            {"id":3, "name":"hadoop article 1", "body":"this is hadoop article 1 body."},
            {"id":4, "name":"hadoop article 2", "body":"this is hadoop article 2 body."}
        ],


    "bdh Videos":
        [
            {"id":5, "name":"bdh videos 1", "body":"this is bdh videos 1 body."},
            {"id":6, "name":"bdh videos 2", "body":"this is bdh videos 2 body."}
        ],
    "hadoop Videos":
        [
            {"id":7, "name":"hadoop videos 1", "body":"this is hadoop videos 1 body."},
            {"id":8, "name":"hadoop videos 2", "body":"this is hadoop videos 2 body."}
        ]
}

<?php

    $videos = '
        {"data":
            {
                "categories":
                {
                    "articles":
                    {
                        "bdh":[],
                        "hadoop":[]
                    },
                    "videos":
                    {
                        "bdhVideos":[],
                        "hadoopVideos":[]
                    }   
                }
            }
        }
    ';

    $details='
        {"details":{
            "bdh":
                [
                    {"id":1, "name":"bdh article 1", "body":"this is bdh article 1 body."},
                    {"id":2, "name":"bdh article 2", "body":"this is bdh article 2 body."}
                ],
            "hadoop":
                [
                    {"id":3, "name":"hadoop article 1", "body":"this is hadoop article 1 body."},
                    {"id":4, "name":"hadoop article 2", "body":"this is hadoop article 2 body."}
                ],


            "bdhVideos":
                [
                    {"id":5, "name":"bdh videos 1", "body":"this is bdh videos 1 body."},
                    {"id":6, "name":"bdh videos 2", "body":"this is bdh videos 2 body."}
                ],
            "hadoopVideos":
                [
                    {"id":7, "name":"hadoop videos 1", "body":"this is hadoop videos 1 body."},
                    {"id":8, "name":"hadoop videos 2", "body":"this is hadoop videos 2 body."}
                ]
            }
        }
    ';

    $arr_videos = json_decode($videos);
    $arr_details = json_decode($details);

    //bdh
    $arr_videos->data->categories->articles->bdh = $arr_details->details->bdh[0];
    //hadoop
    $arr_videos->data->categories->articles->hadoop = $arr_details->details->hadoop[0];

    //videos bdh
    $arr_videos->data->categories->videos->bdh = $arr_details->details->bdhVideos;

    //videos hadoop
    $arr_videos->data->categories->videos->hadoop = $arr_details->details->hadoopVideos;

    print_r($arr_videos);
?>