GUMP::validate_boolean PHP Method

    protected function validate_boolean($field, $input, $param = null)
    {
        if (!isset($input[$field]) || empty($input[$field]) && $input[$field] !== 0) {
            return;
        }
        if ($input[$field] === true || $input[$field] === false) {
            return;
        }
        return array('field' => $field, 'value' => $input[$field], 'rule' => __FUNCTION__, 'param' => $param);
    }