How can I extract and present an object in a json array as a continuous string in php?

I have a json array as below:

{
    "status": 200,
    "bus": [
        {
            "id": "2",
            "route": "1",
            "total_seats": "30",
            "available_seats": [
                "1",
                "2",
                "3",
                "4",
                "5",
                "6",
                "7",
                "8",
                "9",
                "10",
                "11",
                "12",
                "13",
                "14",
                "15",
                "16",
                "17",
                "18",
                "19",
                "20",
                "21",
                "22",
                "23",
                "24",
                "25",
                "26",
                "27",
                "28",
                "29",
                "30"
            ],
            "price": [
                "First Class - 120.00"
            ],
            "departure_time": "20-06-2017, 09:00 AM",
            "arrival_time": "20-06-2017, 09:20 AM",
            "duration": "0 hours<br/>20 minutes"
        },
        {
            "id": "3",
            "route": "1",
            "total_seats": "36",
            "seats_available": 36,
            "available_seats": [
                "1",
                "2",
                "3",
                "4",
                "5",
                "6",
                "7",
                "8",
                "9",
                "10",
                "11",
                "12",
                "13",
                "14",
                "15",
                "16",
                "17",
                "18",
                "19",
                "20",
                "21",
                "22",
                "23",
                "24",
                "25",
                "26",
                "27",
                "28",
                "29",
                "30",
                "31",
                "32",
                "33",
                "34",
                "35",
                "36"
            ],
            "price": [
                "Standard - 50.00"
            ],
            "departure_time": "20-06-2017, 09:00 AM",
            "arrival_time": "20-06-2017, 09:20 AM",
            "duration": "0 hours<br/>20 minutes"
        }
    ]
}

Now i'm trying to extract data from the array and present it as below:

ID:2, Route:1, Total seats: 30, Available seats: 1,2,3,4,5,6,7....30
ID:3, Route:1, Total seats: 36, Available seats: 1,2,3,4,5,6,7....36

So far I have achieved extracting most of the data but I cant seem to to extract the data between "available_seats": []using this code

foreach ($json['bus'] as $bus_data)
    {
    echo "ID".$bus_data['id'].", Route".$bus_data['route'].", Total seats (".$bus_data['total_seats'].", Available seats: ".$bus_data['available_seats'];
    }

What is the best way to achieve extracting and listing the data inside "available_seats": [] as a continuous string as above?