protected function min($key, $length)
    {
        $conCate = (isset($this->errors[$key.self::ERROR])) ?
            $this->errors[$key.self::ERROR].' and ' :
            '';

        //$stringLength = strlen($this->param[$key]);

        //if ($stringLength < (int) $length) {
        if (mb_strlen(trim($this->param[$key])) < $length) {
            $this->errors[$key.self::ERROR] =
                $conCate.ucfirst($this->convertToFieldName($key)).' should be '.__FUNCTION__.'imum '.$length.' characters.';

            return false;
        }

        return true;
    }