public static function cleanPrefix($prefixString)
    {
        $prefixString = trim($prefixString);
        if (empty($prefixString)) {
            return null;
        }

        $result = preg_replace('/_*$/i', '', strtolower($prefixString)) . '_';

        if ($result == '_') {
            return null;
        }

        return $result;
    }