protected function _prepareValue($value)
    {
        if (is_integer($value) || is_float($value)) {
            return $value;
        } elseif (is_bool($value)) {
            return ($value ? 'true' : 'false');
        } elseif (strpos($value, '"') === false) {
            return '"' . $value .  '"';
        } else {
            /** @see Zend_Config_Exception */

            throw new Zend_Config_Exception('Value can not contain double quotes "');
        }
    }