How to do AJAX in jQuery with JSON callback in Zend Framework

<textarea id="mytext">
</textarea>
<input type="button" id="mybutton" value="go" />
 
< script language="Javascript">
//jQuery stuff    
$(document).ready(function() {
    $("#mybutton").click(function() {
        $.post("< ?=$this->baseUrl?>/path/to/my/coolaction",{ 
            mytext: $('#mytext').val()
        }, function(data){
            //alert("Data Loaded: " + data);
            obj = window.eval(data);
            alert("Saved: "+obj['mytext']);
        },"json");
    });
});
< / script>

public function coolAction()
{
     try {
          if ($this->_request->isPost()) {
                 //Do something that will save the $_POST to the database here.
                 $json = Zend_Json::encode($_POST);
                 echo $json;
          } else {
                 throw new Exception ("Invalid action. Not post");
          }
     } catch (Exception $e) {
            echo $e->getMessage();
     }
 
}