Something

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" backgroundAlpha="0" width="730" height="600" applicationComplete="init()">
	<mx:Script>
        <![CDATA[
    private function init():void {
                var loader:URLLoader = new URLLoader();
                var URL:URLRequest = new 
               URLRequest("http://domain.com/xml.php");
                loader.addEventListener(Event.COMPLETE, FillData);
                loader.load(URL);
            }
            private function FillData(event:Event):void {
                var x:XML = new XML(event.target.data);
                xmlout.text = x.output;
            }
        ]]>
    </mx:Script>
<mx:TextInput id="xmlout"/>
</mx:Application>

xml.php
<?php
echo "<data><output>hello world</output></data>";
?>