PHP implements RSS subscription class

<?php
class RSS
{
    /**
    +----------------------------------------------------------
     * RSS频道名
     +----------------------------------------------------------
     */
    protected $channel_title = &#39;&#39;;
    /**
     +----------------------------------------------------------
     * RSS频道链接
     +----------------------------------------------------------
     */
    protected $channel_link = &#39;&#39;;
    /**
     +----------------------------------------------------------
     * RSS频道描述
     +----------------------------------------------------------
     */
    protected $channel_description = &#39;&#39;;
    /**
     +----------------------------------------------------------
     * RSS频道使用的小图标的URL
     +----------------------------------------------------------
     */
    protected $channel_imgurl = &#39;&#39;;
    /**
     +----------------------------------------------------------
     * RSS频道所使用的语言
     +----------------------------------------------------------
     */
    protected $language = &#39;zh_CN&#39;;
    /**
     +----------------------------------------------------------
     * RSS文档创建日期，默认为今天
     +----------------------------------------------------------
     */
    protected $pubDate = &#39;&#39;;
    protected $lastBuildDate = &#39;&#39;;
  
    protected $generator = &#39;YBlog RSS Generator&#39;;
  
    /**
     +----------------------------------------------------------
     * RSS单条信息的数组
     +----------------------------------------------------------
     */
    protected $items = array();
  
    /**
     +----------------------------------------------------------
     * 构造函数
     +----------------------------------------------------------
     * @access public 
     +----------------------------------------------------------
     * @param string $title  RSS频道名
     * @param string $link  RSS频道链接
     * @param string $description  RSS频道描述
     * @param string $imgurl  RSS频道图标
     +----------------------------------------------------------
     */
    public function __construct($title, $link, $description, $imgurl = &#39;&#39;)
    {
        $this->channel_title = $title;
        $this->channel_link = $link;
        $this->channel_description = $description;
        $this->channel_imgurl = $imgurl;
        $this->pubDate = Date(&#39;Y-m-d H:i:s&#39;, time());
        $this->lastBuildDate = Date(&#39;Y-m-d H:i:s&#39;, time());
    }
  
    /**
     +----------------------------------------------------------
     * 设置私有变量
     +----------------------------------------------------------
     * @access public 
     +----------------------------------------------------------
     * @param string $key  变量名
     * @param string $value  变量的值
     +----------------------------------------------------------
     */
     public function Config($key,$value)
     {
        $this->{$key} = $value;
     }
  
    /**
     +----------------------------------------------------------
     * 添加RSS项
     +----------------------------------------------------------
     * @access public 
     +----------------------------------------------------------
     * @param string $title  日志的标题
     * @param string $link  日志的链接
     * @param string $description  日志的摘要
     * @param string $pubDate  日志的发布日期
     +----------------------------------------------------------
     */
     function AddItem($title, $link, $description, $pubDate)
     {
        $this->items[] = array(&#39;title&#39; => $title, &#39;link&#39; => $link, &#39;description&#39; => $description, &#39;pubDate&#39; => $pubDate);
     }
  
     /**
     +----------------------------------------------------------
     * 输出RSS的XML为字符串
     +----------------------------------------------------------
     * @access public 
     +----------------------------------------------------------
     * @return string
     +----------------------------------------------------------
     */
    public function Fetch()
    {
        $rss .= "<?xml version=\"1.0\" encoding=\"utf-8\" ?>\r\n";
        $rss .= "<rss version=\"2.0\">\r\n";
        $rss .= "<channel>\r\n";
        $rss .= "<title><![CDATA[{$this->channel_title}]]></title>\r\n";
        $rss .= "<description><![CDATA[{$this->channel_description}]]></description>\r\n";
        $rss .= "<link>{$this->channel_link}</link>\r\n";
        $rss .= "<language>{$this->language}</language>\r\n";
  
        if (!empty($this->pubDate))
            $rss .= "<pubDate>{$this->pubDate}</pubDate>\r\n";
        if (!empty($this->lastBuildDate))
            $rss .= "<lastBuildDate>{$this->lastBuildDate}</lastBuildDate>\r\n";
        if (!empty($this->generator))
            $rss .= "<generator>{$this->generator}</generator>\r\n";
  
        $rss .= "<ttl>5</ttl>\r\n";
  
        if (!empty($this->channel_imgurl)) {
            $rss .= "<image>\r\n";
            $rss .= "<title><![CDATA[{$this->channel_title}]]></title>\r\n";
            $rss .= "<link>{$this->channel_link}</link>\r\n";
            $rss .= "<url>{$this->channel_imgurl}</url>\r\n";
            $rss .= "</image>\r\n";
        }
  
        for ($i = 0; $i < count($this->items); $i++) {
            $rss .= "<item>\r\n";
            $rss .= "<title><![CDATA[{$this->items[$i][&#39;title&#39;]}]]></title>\r\n";
            $rss .= "<link>{$this->items[$i][&#39;link&#39;]}</link>\r\n";
            $rss .= "<description><![CDATA[{$this->items[$i][&#39;description&#39;]}]]></description>\r\n";
            $rss .= "<pubDate>{$this->items[$i][&#39;pubDate&#39;]}</pubDate>\r\n";
            $rss .= "</item>\r\n";
        }
  
        $rss .= "</channel>\r\n</rss>";
        return $rss;
    }
  
    /**
     +----------------------------------------------------------
     * 输出RSS的XML到浏览器
     +----------------------------------------------------------
     * @access public 
     +----------------------------------------------------------
     * @return void
     +----------------------------------------------------------
     */
    public function Display()
    {
        header("Content-Type: text/xml; charset=utf-8");
        echo $this->Fetch();
        exit;
    }
}
?>