title: How to target specific paragraphs within an HTML string in PHP
body: <p>A simple one for all your PHP guys out there.
  I have a string which represents a portion of HTML. It looks something like this:</p>
  
  <pre><code>&lt;p&gt;blablabla.....&lt;/p&gt;
  &lt;p&gt;blablabla.....&lt;/p&gt;
  &lt;p&gt;blablabla.....&lt;/p&gt;
  &lt;p&gt;blablabla.....&lt;/p&gt;
  &lt;h3&gt;hello&lt;/h3&gt;
  &lt;p&gt;blablabla.....&lt;/p&gt;
  &lt;p&gt;blablabla.....&lt;/p&gt; etc etc
  </code></pre>
  
  <p>What I would like to do is loop over the nodes applying a class to each, until I hit the h3.</p>
  
  <p>Thanks,</p>
  
  <p>EDIT
  I have so far tried:</p>
  
  <pre><code>$dochtml = new DOMDocument();
  $dochtml-&gt;loadHTML($strhtml); 
  
  foreach ($dochtml-&gt;childNodes as $node)
  {
  
      if($node-&gt;tagName == "p") {
      $node-&gt;setAttribute('class', 'someclass');
      } else {
      break;
  }
  }
  </code></pre>
  
  <p>Which simply doesn't work.</p>
  
  <p>The HTML fragment is from a database and represents the editable portion of a page within a CMS.    </p>