title: Bad value for attribute action on element form: Must be non-empty
body: <p>I have a regular form on my php file, after it's submitted it has to echo a message.
  By putting anything in the action="", the only way I can think of displaying a message is by storing it into a session and display it when the page loads if there is a session set.</p>
  
  <p>Everything works fine the way it is right now but w3c validator says I have an error:</p>
  
  <blockquote>
    <p>Bad value  for attribute action on element form: Must be non-empty.</p>
  </blockquote>
  
  <p>How can I fix this error without having to put # or index.php into the action field?</p>
  
  <p>EDIT:</p>
  
  <pre><code>&lt;form action="" method="post"&gt;
      &lt;input type="email" name="email" placeholder="Enter your email"&gt;
      &lt;input type="submit" name="submit" value="SEND"&gt;
  &lt;/form&gt;
  
  &lt;?php
      if(isset($_POST['submit']) &amp;&amp; isset($_POST['email'])){          
          if(filter_var($_POST['email'], FILTER_VALIDATE_EMAIL) === false){
             echo 'This isn\'t a valid email';
          }else{
             echo 'Great';
          }
      }
  ?&gt;
  </code></pre>