title: Why does the W3C Validator not take <?php include() tags in HTML5?
body: <p>I was trying to validate a simple HTML5 page, and it successfully validates everything except three instances of <code>&lt;?php include</code> statements which are marked as errors. I can't figure out what makes it not take the PHP tags. Why would this be? Below are the three errors it outputs:</p>
  
  <pre><code>Validation Output: 3 Errors
  
   Line 29, Column 5: Saw &lt;?. Probable cause: Attempt to use an XML processing instruction in HTML. (XML processing instructions are not supported in HTML.)
              &lt;?php include("inc/main-menu.php"); ?&gt;
  
   Line 87, Column 9: Saw &lt;?. Probable cause: Attempt to use an XML processing instruction in HTML. (XML processing instructions are not supported in HTML.)
          2007-&lt;?php echo date("Y"); ?&gt; 
  
   Line 94, Column 3: Saw &lt;?. Probable cause: Attempt to use an XML processing instruction in HTML. (XML processing instructions are not supported in HTML.)
      &lt;?php include_once("inc/analytics.php"); ?&gt;
  </code></pre>