Formajax:success event not working

Questions
1 
<form id="update_wallet_form" action="update_wallet_amt.php" method="POST" class="form-ajax-submit">
.................................
</form>    
$$('form.form-ajax-submit').on('formajax:success', function (e) {
      var xhr = e.detail.xhr; // actual XHR object

      var data = e.detail.data; // Ajax response from action file
      // do something with response data
    });

Form Ajax Event not working for me. Form is submitting even data is saving through PHP. but formajax:success is not raising.

2

Какой ответ приходит из PHP?

3

PHP query runs successfully. i did not return any value from PHP page.