!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
html xmlns="http://www.w3.org/1999/xhtml">
head>
meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
title>动态显示时间/title>
/head>
script language="javascript">
var xmlHttp;
function createXMLHttpRequest(){
if(window.ActiveXObject){
xmlHttp = new ActiveXObject("microsoft.XMLHTTP");
}
else if(window.XMLHttpRequest){
xmlHttp = new XMLHttpRequest();
}
else{
alert("创建请求失败");
}
}
function sendRequest(){
createXMLHttpRequest();
url = "time_check.php";
xmlHttp.onreadystatechange = callback;
xmlHttp.open('GET',url,true);
xmlHttp.send(null);
}
function callback(){
if(xmlHttp.readyState ==4){
if(xmlHttp.status == 200){
document.getElementById("time").innerHTML = xmlHttp.responseText;
setTimeout("sendRequest()",1000);
}
}
}
/script>
body>
input type="button" value="check it" onclick="sendRequest();" />
br/>
span id="time">/span>
/body>
/html>

?php
header("cache-control:no-cache,must-revalidate"); //取消php页面缓存的设置
header('Content-type: text/html;charset=GB2312');
$showtime = date("北京时间Y年m月d日H:i:s");
echo $showtime;
?>