PHP classes whose name always ends with the word <code>Plugin</code>. The following code shows the source of <code>TimerPlugin.php</code>, the plugin used by <strong>easybook</strong> to measure how long it takes to publish a book:</p>

<div class="code code">
<pre class="code">&lt;?php
namespace Easybook\Plugins;
&nbsp;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Easybook\Events\EasybookEvents as Events;
use Easybook\Events\BaseEvent;
&nbsp;
class TimerPlugin implements EventSubscri