demo01.html
<html>
<head>
<script src="public.js"></script>
<script>
window.onload = function(){
$('username').onblur = function(){
var username = $('username').value;
//var passwd = $('passwd').value;
var xmlHttp = createXMLHttp();
var url = 'demo01.PHP?username=' + username + '&_=' + new Date().getTime();
xmlHttp.open('get',url);
xmlHttp.onreadystatechange = function(){
if(xmlHttp.readyState == 4 && xmlHttp.status == 200){
var flag = xmlHttp.responseText;
if(flag == 1){
//flag = 1表示用户名占用
$('display').innerHTML = "<font color=red>用户名被占用,请更换!</font>";
}
else{
$('display').innerHTML = "<font color=green>用户名可用</font>";
}
}
};
xmlHttp.send(null);
};
};
</script>
</head>
<body>
<form method="psot" action="demo04.PHP">
用户名:<input type="text" id="username" name="username"> <span id="display" ></span>
<br />
密码:<input type="password" id="passwd" name="passwd">
<br />
<input type="submit" value="注册">
<input type="hidden" name="act" value="register">
</form>
</body>
</html>
demo01.PHP
<?PHP
$username = $_GET['username'];
$link = MysqL_connect('127.0.0.1:3306','root','passwd');
MysqL_select_db('test');
MysqL_query('set names utf8');
$result = MysqL_query("select * from admin where username='$username'");
$n = MysqL_num_rows($result);
// $row = MysqL_fetch_row($result);
MysqL_close($link);
if($n > 0){
echo 1;
}
else{
echo 0;
}