def interval_to_milliseconds(interval):
    """Convert a Binance interval string to milliseconds
    :param interval: Binance interval string, e.g.: 1m, 3m, 5m, 15m, 30m, 1h, 2h, 4h, 6h, 8h, 12h, 1d, 3d, 1w
    :type interval: str
    :return:
         int value of interval in milliseconds
         None if interval prefix is not a decimal integer
         None if interval suffix is not one of m, h, d, w
    """
    seconds_per_unit = {
        "m": 60,
        "h": 60 * 60,
        "d": 24 * 60 * 60,
        "w": 7 * 24 * 60 * 60,
    }
    try:
        return int(interval[:-1]) * seconds_per_unit[interval[-1]] * 1000
    except (ValueError, KeyError):
        return None