title: Strip Incomplete HTML Tags using PHP / HTMLPurifier
body: <p>Given the following html:</p>
  
  <pre><code>&lt;p&gt;I am a paragraph&lt;/p&gt;
  
  &lt;ul&gt;
  &lt;li&gt;Item&lt;/li&gt;
  &lt;li&gt;Item 2&lt;/li&gt;
  &lt;/ul&gt;
  
  &lt;div class="special_div_from_email_client"&gt;
  &lt;span&gt;Some text
  </code></pre>
  
  <p>I need to strip out the  tag that is not complete. </p>
  
  <p>What we are trying to do is parse email messages by placing a custom string in the original message so that if it is included in the response it can be stripped out. The assumption is that if the email program enclosed the original message in any html tags, we want to remove the enclosing html tags.</p>