Zend FR

<?php

class IndexController extends Zend_Controller_Action
{

    public function init()
    {
       $this->_helper->contextSwitch()
             ->addActionContext('check', array('xml', 'json'))
             ->initContext();
    }

    public function indexAction()
    {
        // action body
    }

    public function checkAction()
    {
        // action body  
        $request = $this->getRequest()->getPost();

        //referring to the index
        //gets value from ajax request
        $message = $request['message'];

        // makes disable renderer
        $this->_helper->viewRenderer->setNoRender();

        //makes disable layout
        $this->_helper->getHelper('layout')->disableLayout();

        //return callback message to the function javascript
        echo $message; 
    }

}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"       type="text/javascript"></script>

<!--for display text and submit fields i use viewHelpers it's very comfortable  and       easy way.-->
<div class="submit_area">
  <?php echo $this->formText('message', 'empty', array('size' => 32, 'id' => 'message')) ?>
  <?php echo $this->formSubmit('submitTo', 'submit', array('id' => 'submitTo')) ?>
  <div class="show-msg"></div>
</div>

<script >
//for send data i'll use jquery library
$(document).ready( function() {
  //By clicking on button submit condition makes validate on empty message 
  //unless field message will be not empty  , the programm make send data to
  //controller via ajax
  $("#submitTo").click(function() {
    var message = $('#message').val();
    if (message != '') {
      //run ajax 
      $.post('index/check', {'message' : message},
        //callback function
        function (respond) {
          //put respond in class show-msg                          
          $(".show-msg").html(respond);                  
        }
      );
    }
return false;    
  });
});
</script>