JSON Parsing Error: Warning: Attempt to read property on string

Question

I am trying to parse this JSON from a Football API using PHP.

Below is a subset of the JSON output.

Specifically, I am trying to get the fixture id (eg. 198772) from the below json.

$json = '{
    "get": "predictions",
    "parameters": {
        "fixture": "198772"
    },
    "errors": [],
    "results": 1,
    "paging": {
        "current": 1,
        "total": 1
    },
    "response": [{
        "predictions": {
            "winner": {
                "id": 1189,
                "name": "Deportivo Santani",
                "comment": "Win or draw"
            },
            "win_or_draw": true,
            "under_over": "-3.5",
            "goals": {
                "home": "-2.5",
                "away": "-1.5"
            },
            "advice": "Combo Double chance : Deportivo Santani or draw and -3.5 goals",
            "percent": {
                "home": "45%",
                "draw": "45%",
                "away": "10%"
            }
        }
    }]
}';

$response = json_decode($json);
echo "Output: ". $response[0]->fixture; 

When I tried to run my codes, I encounter this error:

Attempt to read property "fixture" on string in C:\xampp\htdocs\xampp\livescore\api-test\predictions.php on line 90

This is the liner that is throwing up the error:

    echo "Output: ". $response[0]->fixture;

Any idea why this is happening? Any help or insights is much appreciated.