simpleXML pre check it's a feed
<p>I have a random url, set as a string in PHP, Example:</p>

<pre><code>$u='http://www.google.com/feedtest/something';
</code></pre>

<p>I am using simpleXML to get the feed from <code>$u</code></p>

<p>How would you identify if the url is a feed (RSS,XML, ..) before downloading it with simpleXML?</p>
