Echo a random variable
<p>I'm trying to create a random script for thumbnails in my wordpress theme
the problem here's that I cannot put an echo inside the add_image_size() but also if I write $wds it doesn't randomize the stuff and I'm completely lost. 
Can somebody give a hand on this one, please?
Thank you!</p>

<p>here's my code:</p>

<pre><code>&lt;?php 
$wds = array('100', '150', '200');
echo $wds[rand(0, count($wds)-1)];
?&gt;

&lt;?php add_image_size('mosaics', $wds, 0, false); ?&gt;
</code></pre>
