What is the best open source application written in PHP to reference for 'good code'?
<p>So I've read Drupal, Joomla, Magento, Wordpress all have bad PHP code... which is a shame because I was referring to them to see 'what they did' so I could hopefully get some insight. I assumed popular software meant it would have decent coding.</p>

<p>So, what is the best PHP open source application to study?</p>
