PHPAccessArray.php

<?php

$json = '{
    "Message360": {
        "ResponseStatus": 0,
        "Errors": {
            "Error": [
                {
                    "Code": "ER-M360-EML-104",
                    "Message": "Please enter a correctly formatted  email address.",
                    "MoreInfo": []
                }
            ]
        }
    }
}';

$array = json_decode($json, true);

echo $array['Message360']['Errors']['Error'][0]["Code"];