<blockquote>
  <h2 id="thisisaheader">This is a header.</h2>
  <ol>
    <li>This is the first list item.</li>
    <li>This is the second list item.</li>
  </ol>
  <p>Here's some example code:</p>
    <pre><code>return shell_exec("echo $input | $markdown_script");
    </code></pre>
</blockquote>