//该文件为register.php,在客户端<html><head><title>用户注册</title><meta http-equiv = "content-type" content = "text/html;charset=utf-8"/><script type = "text/javascript" >//创建ajax引擎function getXmlHttpObject(){var xmlHttpRequest;//不同浏览器获取对象XmlHttpRequest对象方法不同if(window.ActiveXObject){xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");}else{xmlHttpRequest = new XMLHttpRequest();}return xmlHttpRequest;}var myXmlHttpRequest = "";//验证用户名是否存在function checkName(){//1号线myXmlHttpRequest = getXmlHttpObject();//判断创建成功？if(myXmlHttpRequest){//通过myXmlHttpRequest对象发送请求到服务器的某个页面//第一个参数表示请求的方式, "get"/"post"//第二个参数指定url,对哪个页面发出ajax请求(本质仍然是HTTP请求)//第三个参数.true表示使用异步机制，false表示不使用异步机制//注意：此处如果"username"和"="之间有空格，否则会出错，在服务器端接收不到"username";//注意：如果"="之后有空格则将此空格也作为接收到的username的值的一部分。//即在服务器端收到的username的值=“ ”(即空格)+从客户端发送的username值。var url = "/AjaxTest/registerProcess.php?username=" + $("username1id").value;//window.alert(url);//打开请求myXmlHttpRequest.open("get",url,true);//指定回调函数.process是个函数名myXmlHttpRequest.onreadystatechange = process;//真正发送请求。如果是get请求则填入null即可//如果是post请求，则填入实际的数据//2号线myXmlHttpRequest.send(null);}}//回调函数function process(){//window.alert("这是回调函数" + myXmlHttpRequest.readyState);//我要取出从registerProcess.php页面返回的数据if(myXmlHttpRequest.readyState == 4){//取出值，根据返回信息的格式而定//window.alert("服务器返回" + myXmlHttpRequest.responseText);//4号线$('myResponse').value = myXmlHttpRequest.responseText;}}function $(id){return document.getElementById(id);}</script></head><body><form action = "" method = "post">用户名：<input type = "text" name = "username1" id = "username1id" ><input type = "button" onclick = "checkName();" value = "验证用户名"><input style = "border-width: 0; color: red" type = "text" id = "myResponse"><br/>密码：<input type = "password" name = "password"><br/>电子邮件:<input type = "text" name = "email"><br/><input type = "submit" value = "用户注册"></form><form action = "" method = "post">用户名：<input type = "text" name = "username2" ><br/>密码：<input type = "password" name = "password"><br/>电子邮件:<input type = "text" name = "email"><br/><input type = "submit" value = "用户注册"></form></body></html>//该文件为registerProcess.php,在服务器端<?php//接收数据$username = $_GET["username"];if($username=="shunping"){echo "用户名不可用";}else{echo "用户名可用";}echo "用户名：".$username;//3号线?>
