客户端代码：
代码如下：

!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无标题文档/title
/head
script language="javascript"
var xmlHttp;

function createXMLHttpRequest(){
if(window.ActiveXObject){
xmlHttp = new ActiveXObject("microsoft.XMLHTTP");
}
else if(window.XMLHttpRequest){
xmlHttp = new XMLHttpRequest();
}

}

function sendRequest(){

createXMLHttpRequest();

var name = document.getElementById("name").value;
url = "String_check.php?page="+name;
xmlHttp.onreadystatechange = callback;
xmlHttp.open('GET',url,true);
xmlHttp.send(null);
}

function callback(){
if(xmlHttp.readyState == 4){
if(xmlHttp.status == 200){
document.getElementById("show").innerHTML = "您输入的字符串为："+ xmlHttp.responseText;

}
}
}

/script
body
pAJAX test;/p
pbr/
input type="text" id="name" onkeyup="sendRequest();" /
br/
span id="show"/span
/p
/body
/html


服务器端代码：
代码如下：

?php
header('Content-type: text/html;charset=GB2312');
$ename = $_GET["page"];
if ($ename == "") {
$ename = "请输入：";
}
echo ($ename);
exit(0);
?