I have from a xml api this:

```
<artist>    
  <name>David Guetta & Afrojack</name>
  <url>http://www.last.fm/music/David+Guetta+&+Afrojack</url>
  <image size="small">http://userserve-ak.last.fm/serve/34/67755308.jpg</image>
  <image size="medium">http://userserve-ak.last.fm/serve/64/67755308.jpg</image>
</artist>

```

I parse the name and url to PHP in this way:

```
$xml=simplexml_load_file('api.xml');
$name=$xml->artist->name;
$url=$xml->artist->url;

```

How do I get the url of the image in medium size?