我只使用simplepie解析itunes提要，我想提取im：rating：
<entry>
<updated>2014-04-18T04:44:00-07:00</updated>
<id>978910847</id>
<title>anything</title>
<content type="text">
any description here
</content>
<im:contentType term="Application" label="Application"/>
<im:voteSum>0</im:voteSum>
<im:voteCount>0</im:voteCount>
<im:rating>5</im:rating>
<im:version>1.5</im:version>
<author>
<name>any name</name>
<uri>https://itunes.apple.com/us/reviews/id</uri>
</author>
<link rel="related" href="https://itunes.apple.com/us/review?id=&type=Purple%20Software"/>
<content type="html"></content>
</entry>
有什么想法吗？
谢谢！