代码如下
先建立一个表单
<html>
<head>
<meta http-equiv="Content-Type"
content="text/html;charset=UTF-8"/>
<script type="text/javascript"
src="ajax.js"></script>
</head>
<body>
<form action="" >
用户名: <input type="text" name="user" id=""
onblur="sendParam(this.value)"/>
<span style="color: red;font-size:
14px" id="tishi"></span>
<br/>
密 码: <input
type="password" name="mima"/> <br/>
<input type="submit" value="提交"
name="submit"/>
</form>
</body>
</html>
然后
数据库的基本语言
<?php
if(isset($_GET[‘user‘])){
$user = $_GET[‘user‘];
$conn = mysql_connect("localhost","root","") or
die("数据库连接失败".mysql_error());
mysql_select_db("test");
mysql_query("set names ‘utf8‘");
$sql = "select count(*) from bbs where userName=‘$user‘";
$result = mysql_query($sql);
$row = mysql_fetch_row($result);
if($row[0]){
echo "该用户名已经被注册";
}else{
echo
"该用户名还没有被使用过,可以注册";
}
}
?>
最后AJAX
var xmlHttp;
function getXmlHttp(){
if(window.ActiveXObject){
xmlHttp = new
ActiveXObject("MICROSOFT.XMLHTTP");
}else if(window.XMLHttpRequest){
xmlHttp = new XMLHttpRequest();
}
}
function sendParam(url){
getXmlHttp();
xmlHttp.open("GET","check.php?user="+url,true);
//
setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xmlHttp.onreadystatechange = getTxt;
xmlHttp.send(null);
}
function
getTxt(){
if(xmlHttp.readyState == 4){
if(xmlHttp.status ==
200){
var sp = document.getElementById("tishi");
sp.innerHTML = xmlHttp.responseText;
}
}
}
原文地址：http://www.cnblogs.com/gx9401142810/p/3735644.html
