title: when validating at w3c it is not recognizing the alt attribute when echo php $image
body: <p>I have an page for viewing posters with the following code:</p>
  
  <pre><code>&lt;div class="img"&gt;&lt;img src="&lt;?= $image; ?&gt;" alt="" /&gt;&lt;/div&gt;
  </code></pre>
  
  <p>but when I validate it at w3c it could not find the alt attribute. 
  maybe I have to escape the PHP element in someway?</p>
  
  <p>How could I do that?</p>
  
  <p>The error I get:</p>
  
  <blockquote>
    <p>An img element must have an alt attribute, except under certain
    conditions. For details, consult guidance on providing text
    alternatives for images.</p>
  </blockquote>