What causes an error when changing the value in json?

Question

PHP

JSON:

"USD": {
        "Value": 71.4783,
        "Previous": 71.0863
    },

PHP:

$data  = file_get_contents('values.json');
    $data = json_decode($data , true); 
    $data['USD']['Value'] = "2";
    $data = json_encode($data);
    file_put_contents('values.json', $data);

Error: Uncaught Error: Cannot use string offset as an array in

Answer 1

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$data  = file_get_contents('values.json');
$data = json_decode($data , true); 
var_dump($data);

Answer 2

It looks like you have an extra comma in your JSON file. In the end.