Create or upgrade json object PHP array

Got this playlist json:

{
  "SyncInterval": 10000,
  "Tasks": [
    {
      "Stream": "LiveApp/playlist1",
      "Blocks": [
        {
          "Id": 201,
          "MaxIterations": 0,
          "Name": "Block-1",
          "Streams": [
            {
              "Type": "vod",
              "Source": "/samba/my/7v2qgkv.mp4"
            },
            {
              "Type": "vod",
              "Source": "/samba/my/7svzmsi.mp4"
            }
          ]
        }
      ]
    }
  ]
}

---

I want to create a new task with PHP array.
like this:

{
      "Stream": "LiveApp/playlist2",
      "Blocks": [
        {
          "Id": 905,
          "MaxIterations": 0,
          "Name": "Block-1",
          "Streams": [
            {
              "Type": "vod",
              "Source": "/samba/my2/7v2q2343232.mp4"
            }
          ]
        }
      ]
    }

---

So result will be:

{
  "SyncInterval": 10000,
  "Tasks": [
    {
      "Stream": "LiveApp/playlist1",
      "Blocks": [
        {
          "Id": 201,
          "MaxIterations": 0,
          "Name": "Block-1",
          "Streams": [
            {
              "Type": "vod",
              "Source": "/samba/my/7v2qgkv.mp4"
            },
            {
              "Type": "vod",
              "Source": "/samba/my/7svzmsi.mp4"
            }
          ]
        }
      ]
    },
    {
      "Stream": "LiveApp/playlist2",
      "Blocks": [
        {
          "Id": 905,
          "MaxIterations": 0,
          "Name": "Block-1",
          "Streams": [
            {
              "Type": "vod",
              "Source": "/samba/my2/7v2q2343232.mp4"
            }
          ]
        }
      ]
    }
  ]
}

---

Then, update the array with new “Sources” WHERE the “Stream”: “LiveApp/playlist1” or “Stream”: “LiveApp/playlist2”, as playlist1 and playlist2 where 2 different users.