save button for xml doesn't work.

Scheduler Javascript
#1

I try to save my events to xml file, but the save button doesn’t work.
Console says,
Uncaught TypeError: Object # has no method ‘toXML’

My codes are here.

---------------------mainCalendar.jsp------------------------------

html,body { margin: 0px; padding: 0px; height: 500; overflow: hidden; } <%-- save 버튼 --%>
 
 
		<div class="dhx_cal_tab" name="day_tab" style="right: 204px;"></div>
		<div class="dhx_cal_tab" name="week_tab" style="right: 140px;"></div>
		<div class="dhx_cal_tab" name="month_tab" style="right: 76px;"></div>
	</div>
	<div class="dhx_cal_header"></div>
	<div class="dhx_cal_data"></div>

</div>

----------------xml_writer.php---------------------------

<?php file_put_contents("data.xml",$_POST["data"]); ?>
#2

Be sure that you have the next script tag on the page ( after dhtmlxscheduler.js )

<script src='codebase/ext/dhtmlxscheduler_serialize.js'></script>