html & javascript
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script language = 'javascript'>
//创建XMLHttpRequest对象实例,反正都差不多，省略
//startRequest函数,
function startRequest(username)
{
createXMLHttpRequest();
xmlHttp.open("GET","ckuser.php?name="+username,true);
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.send(null);
}
function handleStateChange()
{
if(xmlHttp.readyState==4)
{
if(xmlHttp.status==200)
{
//在这里alert xmlhttp.responseText 出来 已经取出 yes or no
//但是xmlHttp.resposeText好像既不等于字符串yes 也不等于字符串no
//这两个if 语句都直接跳过了
if (xmlHttp.responseText=="yes")
{
document.getElementById("ckuser").innerHTML = '被注册';
} else if (xmlHttp.responseText=="no")
{
document.getElementById("ckuser").innerHTML = '未注册';
}
}
}
}
</script>
//省略部分HTML代码
<input type="text" name="username" value="" />
//省略部分HTML代码
php函数
<?php
$username = $_GET["name"];
$link = mysql_connect('localhost:3306', 'root', '123456')
or die('Could not connect: ' . mysql_error());
mysql_select_db('star') or die('Could not select database');
$query="select id from users where username='".$username."';";
$res=mysql_query($query) or die('Query failed: ' . mysql_error());
if(mysql_num_rows($res)!=0)
{
echo "yes";
}else
{
print "no";
}
?>
