php制作基于xml的RSS订阅源功能示例有哪些？

<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0" xmlns:wfw="http://wellformedweb.org/CommentAPI/"></rss>

<?php 
class Rss{
 protected $dom = null;
 protected $temp = './feed.xml';
 protected $rss = null;
 protected $title = '';
 protected $desc = '';
 protected $link = '';
 public function __construct(){
  $this->title = '物理学';
  $this->desc = '现代物理学';
  $this->link = 'http://mysql/rss.php';
  $this->dom = new DOMDocument('1.0','utf-8');
  $this->dom->load($this->temp);
  $this->rss = $this->dom->getElementsByTagName('rss')->item(0);
 }
 public function feed($arr){
  $this->createChannel();
  $channel = $this->dom->getElementsByTagName('channel')->item(0);
  foreach ($arr as $v){
   $channel->appendChild($this->createItem($v));
  }
  header('content-type:text/xml');
  echo $this->dom->savexml();
 }
 protected function createChannel(){
  $channel = $this->dom->createElement('channel');
  $channel->appendChild($this->createEle('title',$this->title));
  $channel->appendChild($this->createEle('link',$this->link));
  $channel->appendChild($this->createEle('description',$this->desc));
  $this->rss->appendChild($channel);
 }
 protected function createItem($arr){
  $item = $this->dom->createElement('item');
  foreach($arr as $k => $v){
   $item->appendChild($this->createEle($k,$v));
  }
  return $item;
 }
 protected function createEle($name,$value){
  $e=$this->dom->createElement($name);
  $t=$this->dom->createTextNode($value);
  $e->appendChild($t);
  return $e;
 }
}
$arr = array(
 array(
  'title'=>'牛顿力学',
  'link'=>'1',
  'description'=>'牛顿力学'
 ),
 array(
  'title'=>'相对论',
  'link'=>'1',
  'description'=>'爱因斯坦的相对论'
 )
);
$rss = new Rss;
$rss->feed($arr);
?>