title: What is the difference between php and html file extensions?
body: <p>I am having a <code>.php</code> file with the following code. While I am changing the extension of the file as <code>.html</code> then also it is behaving in the same way. Can anyone explain the following:</p>
  
  <ol>
  <li>Why the file is behaving in the same manner with both the
  extensions?</li>
  <li>What is the difference between the <code>.php</code> and <code>.html</code> file extensions?</li>
  </ol>
  
  <p><code>.php</code> file</p>
  
  <pre><code>&lt;html&gt;
  
       &lt;head&gt;
            &lt;!-- some html code --&gt;
       &lt;/head&gt;
  
       &lt;body&gt;
            &lt;?php echo "Hello!" ?&gt;
       &lt;/body&gt;
  
  &lt;/html&gt;
  </code></pre>