Keys in PHP array are not sorted numerically
<p>I have a PHP array with keys that contain a year and week number like so:</p>

<pre><code>year-week
</code></pre>

<p>Using the built in ksort function it's returning them like so:</p>

<pre><code>ksort($array);

2011-21
2011-3
2011-44
2011-45
</code></pre>

<p>Is it possible to have them sorted numerically like so:</p>

<pre><code>2011-3
2011-21
2011-44
2011-45
</code></pre>
