RSS php RSS生成类

/* E X A M P L E -----------------------------------------------
        $feed = new RSS();
        $feed->title       = "RSS Feed Title";
        $feed->link        = "http://website.com";
        $feed->description = "Recent articles on your website.";

        $db->query($query);
        $result = $db->result;
        while($row = mysql_fetch_array($result, MYSQL_ASSOC))
        {
            $item = new RSSItem();
            $item->title = $title;
            $item->link  = $link;
            $item->setPubDate($create_date); 
            $item->description = "<![CDATA[ $html ]]>";
            $feed->addItem($item);
        }
        echo $feed->serve();
    ---------------------------------------------------------------- */

    class RSS
    {
        var $title;
        var $link;
        var $description;
        var $language = "en-us";
        var $pubDate;
        var $items;
        var $tags;

        function RSS()
        {
            $this->items = array();
            $this->tags  = array();
        }

        function addItem($item)
        {
            $this->items[] = $item;
        }

        function setPubDate($when)
        {
            if(strtotime($when) == false)
                $this->pubDate = date("D, d M Y H:i:s ", $when) . "GMT";
            else
                $this->pubDate = date("D, d M Y H:i:s ", strtotime($when)) . "GMT";
        }

        function getPubDate()
        {
            if(empty($this->pubDate))
                return date("D, d M Y H:i:s ") . "GMT";
            else
                return $this->pubDate;
        }

        function addTag($tag, $value)
        {
            $this->tags[$tag] = $value;
        }

        function out()
        {
            $out  = $this->header();
            $out .= "<channel>\n";
            $out .= "<title>" . $this->title . "</title>\n";
            $out .= "<link>" . $this->link . "</link>\n";
            $out .= "<description>" . $this->description . "</description>\n";
            $out .= "<language>" . $this->language . "</language>\n";
            $out .= "<pubDate>" . $this->getPubDate() . "</pubDate>\n";

            foreach($this->tags as $key => $val) $out .= "<$key>$val</$key>\n";
            foreach($this->items as $item) $out .= $item->out();

            $out .= "</channel>\n";

            $out .= $this->footer();

            $out = str_replace("&", "&amp;", $out);

            return $out;
        }

        function serve($contentType = "application/xml")
        {
            $xml = $this->out();
            header("Content-type: $contentType");
            echo $xml;
        }

        function header()
        {
            $out  = '<?xml version="1.0" encoding="utf-8"?>' . "\n";
            $out .= '<rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/">' . "\n";
            return $out;
        }

        function footer()
        {
            return '</rss>';
        }
    }

    class RSSItem
    {
        var $title;
        var $link;
        var $description;
        var $pubDate;
        var $guid;
        var $tags;
        var $attachment;
        var $length;
        var $mimetype;

        function RSSItem()
        { 
            $this->tags = array();
        }

        function setPubDate($when)
        {
            if(strtotime($when) == false)
                $this->pubDate = date("D, d M Y H:i:s ", $when) . "GMT";
            else
                $this->pubDate = date("D, d M Y H:i:s ", strtotime($when)) . "GMT";
        }

        function getPubDate()
        {
            if(empty($this->pubDate))
                return date("D, d M Y H:i:s ") . "GMT";
            else
                return $this->pubDate;
        }

        function addTag($tag, $value)
        {
            $this->tags[$tag] = $value;
        }

        function out()
        {
            $out .= "<item>\n";
            $out .= "<title>" . $this->title . "</title>\n";
            $out .= "<link>" . $this->link . "</link>\n";
            $out .= "<description>" . $this->description . "</description>\n";
            $out .= "<pubDate>" . $this->getPubDate() . "</pubDate>\n";

            if($this->attachment != "")
                $out .= "<enclosure url='{$this->attachment}' length='{$this->length}' type='{$this->mimetype}' />";

            if(empty($this->guid)) $this->guid = $this->link;
            $out .= "<guid>" . $this->guid . "</guid>\n";

            foreach($this->tags as $key => $val) $out .= "<$key>$val</$key\n>";
            $out .= "</item>\n";
            return $out;
        }

        function enclosure($url, $mimetype, $length)
        {
            $this->attachment = $url;
            $this->mimetype   = $mimetype;
            $this->length     = $length;
        }
    }