title: cannot get a response from jquery / ajax
body: <p>This is giving me headaches, AGAIN. I either don't understand this ajax response stuff at all, or it's poorly coded.</p>
  
  <p>Let's establish an <strong>extremely simple</strong> example to work with:</p>
  
  <p>register.php:</p>
  
  <pre><code>&lt;?php
  echo 'I want some response !!';
  ?&gt;
  </code></pre>
  
  <p>ajax call:</p>
  
  <pre><code>$.ajax({
   url: '/register.php',
   type: 'POST',
   data: $('#form-registracia').serializeArray(),
   success: function(e){
     var response = e.responseText;
     alert(response);
   }
  });
  </code></pre>
  
  <p>Alert says <strong>undefined</strong>. Why? I tried messing with it for hours now, I read the jquery site, nothing helps. I'm sure the PHP file gets executed and that the echo is sent back to ajax.</p>
  
  <p>Thanks in advance!</p>