title: How does yui3 io-form return failure or success?
body: <p>I have the following:</p>
  
  <pre><code>YUI().use("io-form",
      function(Y) {
          var cfg = {
              method: 'POST',
              form: {
                  id: 'subscribe-form',
                  useDisabled: false
              }
          };
          function login() {
              Y.io('process.php', cfg);
              Y.on('io:success', onSuccess, this);
              Y.on('io:failure', onFailure, this);
          };
          function onSuccess(id,response,args) {
              document.getElementById('myformmsg').innerHTML = response.responseText;
              document.forms['myform'].reset();
          };
          function onFailure(id,response,args) {
              document.getElementById('myformmsg').innerHTML = "Error, retry...";
              document.forms['myform'].reset();
          };
          Y.on('click', login, '#myformbutton', this, true);
  });
  </code></pre>
  
  <p>How does yui know whether to go into onSucces of onFailure. What do I have to return from PHP?</p>