code: public function set($name, $value, $expire = null)
      {
          if ($expire === null) {
              $expire = $_SERVER['REQUEST_TIME'] + 2592000;   //a month
          }
  
          return setcookie(
              $name,
              $value,
              $expire,
              $this->config['path'],
              $this->config['domain'],
              $this->config['secure'],
              $this->config['httponly']
          );
      }
docs: 设置COOKIE
  
  @param string $name 待设置的COOKIE名字
  @param string|int $value 建议COOKIE值为一些简单的字符串或数字，不推荐存放敏感数据
  @param int $expire 有效期的timestamp，为NULL时默认存放一个月
  @param boolean
  @return bool