php+js+mysql设计的仿webQQ-<1>邮箱验证

function checkEmail(Email)
{
var xmlhttp;
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
if(xmlhttp.overrideMimeType)
{//设置MIME类别
xmlhttp.overrideMimeType("text/xml");
}
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
var url="checkEmail.php?email="+document.getElementById("email").value;    //转到checkEmail.php进行验证
xmlhttp.open("GET",url,true);
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("error1").innerHTML=xmlhttp.responseText;
}
}
xmlhttp.send(null);
}

<?php
header('Content-Type:text/html;charset=GB2312');    //编码方式设置
include("conn.php");
$email=$_GET["email"];
$len=strlen($email);
if($email==null)
{
echo "<font color=red size=2px>*邮箱不能为空！</font>";
}
else
{
if($len>50)
{
echo "<font color=red size=2px>*邮箱不要超过50个字符！</font>";
}
else
{
if(eregi("^[_.0-9a-z-]+@([0-9a-z][0-9a-z-]+.)+[a-z]{2,3}$",$email))    //在php中用正则表达式验证邮箱
{
$sql="select * from user where email='$email'";     //连接数据库进行查询看邮箱是否被用
$result = mysql_query($sql);
$num=mysql_num_rows($result);
if($num>0)
{
echo "<font color=red size=2px>*该邮箱已被用！</font>";
}
else
{
echo "<font color=green size=2px>*邮箱可用！</font>";
}

}
else
{
echo "<font color=red size=2px>*该邮箱不可用！</font>";
}
}
}
?>