title: Echo command doesn't do anything
body: <p>I've been started studying PHP in my spare time, and the first code example I was given was this:</p>
  
  <pre><code>&lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"&gt;
  &lt;html&gt;
      &lt;body&gt;
          &lt;?php
          echo "Hello World";
          ?&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>From what I understand, this should write out "Hello World". However, all I see is a blank webpage. Any ideas why this is and how I should go about fixing it?</p>