How do I convert the given JSON array to more specified JSON array given below?

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PHP

JSON

<?php
include '../dbconfig.php';
$currentbooking="Some Mysqli Query";

$result = mysqli_query($link, $currentbooking);
$response = array();
while($row = mysqli_fetch_assoc($result))
{
$response[]=$row;
}
echo json_encode($response);
?>
I am getting response as below
[
{
"id": "3",
"diag_name": "LT Diagnostics",
"test_name": "Alk PO4",
"booking_date": "2018-05-20"
},
{
"id": "3",
"diag_name": "LT Diagnostics",
"test_name": "CRP",
"booking_date": "2018-05-20"
},
{
"id": "4",
"diag_name": "Seepz Diagnostics",
"test_name": "Alk PO4",
"booking_date": "2018-05-21"
}
]
But i want a more justified json array written below.

[
{
"diag_name": "LT Diagnostics",
"test_name": [
{
"id": "3",
"name" : "Alk PO4"
},
{
"id": "3",
"name" : "CRP"
}
],
"booking_date": "2018-05-20"
},
{
"diag_name": "Seepz Diagnostics",
"test_name": [
{
"id": "4",
"name" : "Alk PO4"
}
],
"booking_date": "2018-05-21"
},

]

What I have tried:

Plz I don't have any idea how to get the specified JSON array.Plz help me with how to go with it.I want the specified JSON format in PHP.
I am using Core PHP