Why isn't my variable expanded in this string?
<pre><code>$q = $_GET['q'];

// Load and parse the XML document 

$rss =  simplexml_load_file('http://search.twitter.com/search.atom?lang=en&amp;q=$q&amp;rpp=100&amp;page=1');
</code></pre>

<p>This returns results containing <code>"$q"</code> instead of results containing the value of <code>$q</code>. Why won't it work?</p>
