正则表达实现rss解析

<?PHP
$str='<title>Our Demo RSS</title>
      <link>http://www.tracypeterson.com/RSS/RSS.PHP</link>
      <description>A Test RSS</description>
      <language>en-us</language>
      <pubDate>$Now</pubDate>
      <lastBuildDate>$Now</lastBuildDate>
      <docs>http://someurl.com</docs>
      <managingEditor>you@youremail.com</managingEditor>
      <webMaster>you@youremail.com</webMaster>';
preg_match_all('/tle>(.*)</',$str,$v[0]);
preg_match_all('/ocs>(.*)</',$v[1]);
preg_match_all('/ion>(.*)</',$v[2]);
for($j=0;$j<3;$j++)
{
	var_dump($v[$j][1]);
	echo "<br>";
}
?>