实只要简单的实现ajax的检测用户名，正规点要分三个文件。我这里简单点:
第一个：index.php
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.hake.cc/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.hake.cc/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script language="javascript" src=http://www.phpzy.com/PHPjichu/"ajax.js"></script>
</head>
<body>
<table align="center">
<tr>
<td width="25%" class="altbg1"> 用 户 名<font color="red">*</font>
<input size="25" name="username" id="username" type="text" value="" onblur="startRequest(document.getElementById('username').value);" /><br /></td>
<td></td>
<td id="ckuser"></td>
</tr>
</table>
</body>
</html>
第二个要用到js：ajax.js
[php]
var xmlHttp;
function createXMLHttpRequest()
{
if(window.XMLHttpRequest)
{
xmlHttp = new XMLHttpRequest();//mozilla浏览器
}
else if(window.ActiveXObject)
{
try
{
xmlHttp = new ActiveX0bject("Msxml2.XMLHTTP");//IE老版本
}
catch(e)
{}
try
{
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");//IE新版本
}
catch(e)
{}
if(!xmlHttp)
{
window.alert("不能创建XMLHttpRequest对象实例");
return false;
}
}
}
function startRequest(username)
{
createXMLHttpRequest();//特编
xmlHttp.open("GET","ckuser.php?name="+username,true);
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.send(null);
}
function handleStateChange()
{
if(xmlHttp.readyState==4)
{
if(xmlHttp.status==200)
{
//alert("来自服务器的响应：" + xmlHttp.responseText);
if(xmlHttp.responseText == "true"){
document.getElementById("ckuser").innerHTML = '此用户名以被人注册';
}
else if(xmlHttp.responseText == "false")
{
document.getElementById("ckuser").innerHTML = '检测通过';
}
}
}
}
[/php]
第三个文件就是php文件:ckuser.php
<?php
require_once("conn.php");
$username = $_GET["name"];
$query="select id from user where username='".$username."';";
$res=mysql_query($query);
if(mysql_num_rows($res)!=0)
{
echo "true";
}else
{
echo "false";
}
?>
最后一个是数据库链接文件conn.php
<?php
$conn=mysql_connect("localhost","root","l1314520") or die("数据库服务器连接错误".mysql_error());
mysql_select_db("test",$conn) or die("数据库访问错误".mysql_error());
mysql_query("set character set gb2312");
mysql_query("set names gb2312");
?>
