跪求ajax问题

天台的故事 2014-12-09 11:37:58



<!DOCUTYPE html>

<html>

	<head>

		<title>聊天窗口</title>

		<meta http-equiv="Content-type" content="text/html; charset=UTF-8">

	</head>

	<script type="text/javascript">

	 window.resizeTo(580,650);

	 window.setInterval("getMessage()", 3000);

	 

	 function getXmlHttpObject(){

		var xmlHttpRequest;

		//不同的浏览器获取对象xmlhttprequest对象方法不一样

		if(window.ActiveXObject){

			xmlHttpRequest =new ActiveXObject("Microsoft.XMLHTTP");

		}else{

			xmlHttpRequest =new XMLHttpRequest();

		}

		return xmlHttpRequest;

	}



	function getMessage()

	{

		var myXmlHttpRequest = getXmlHttpObject();



	 	if(myXmlHttpRequest)

	 	{

	 		var url = "getMessage.php";

	 		var data = "getter=<?php @session_start(); echo $_SESSION['username'];?>&sender=<?php echo $_GET['username'];?>";



	 		myXmlHttpRequest.open("post",url,true);

	 		myXmlHttpRequest.setRequestHeader("Content-type","application/x-www-form-urlencoded");



	 		myXmlHttpRequest.onreadystatechange=function()

	 		{

		 		if(myXmlHttpRequest.readyState==4)

		 		{

		 			if(myXmlHttpRequest.status==200)

		 			{

		 				//接收

		 				var mes=myXmlHttpRequest.responseXML;

		 				

		 				window.alert(mes);  //这里打印出来老是为null

		 			}

		 		}

	 		}

	 		myXmlHttpRequest.send(data);

	 	}



	}



	 function sendMessage()

	 {

	 	var myXmlHttpRequest = getXmlHttpObject();



	 	if(myXmlHttpRequest)

	 	{

	 		var url = "sendMessage.php";

	 		var data = "con=" + $('con').value +"&getter=<?php echo $_GET['username'];?>"+"&sender=<?php @session_start(); echo $_SESSION['username'];?>";



		 	myXmlHttpRequest.open("post",url,true);

		 	myXmlHttpRequest.setRequestHeader("Content-type","application/x-www-form-urlencoded");

		 	myXmlHttpRequest.onreadystatechange=function()

		 	{

		 		if(myXmlHttpRequest.readyState==4)

		 		{

		 			if(myXmlHttpRequest.status==200)

		 			{



		 			}

		 		}

		 	}

		 	myXmlHttpRequest.send(data);

	 	}

	

	 }



	 function $(id)

	 {

		return document.getElementById(id);

	 }

	</script>

	<body>

		<center>

			<h2><span style="color:red;"><?php @session_start(); echo $_SESSION['username'];?></span>跟<span style="color:red;"><?php echo $_GET['username'];?></span>聊天</h2>

			<textarea name="context" rows="20" cols="70"></textarea><br/>

			<input style="width:300px" type="text" name="sendcontext" id="con">

			<input type="button" name="send" onclick="sendMessage();" value="发送">

		</center>

	</body>



</html>

上面的getMessage()函数是获取ajax查找出来的数据,getMessage()函数里面的.onreadystatechange指定的回调函数中window.alert(mes);打印出来老是为空，但是我ajax请求的getMessage页面有返回<xml>数据啊，下面是ajax请求getMessage的代码



<?php

	include "MessageServer.class.php";

	@header( 'Content-Type:text/xml;charset=utf-8'); 

	@header("Cache-Control: no-cache");

	$getter = $_POST['getter'];

	$sender = $_POST['sender'];



	//调用MessageSerive获取信息

	$messageServer = new MessageServer();



	$messList = $messageServer->getMessage($getter, $sender);



	echo $messList;

	

?>

echo $messLis t是有数据输出的,输出的是<mess></mess>

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