php js 跳转不了是为什么阿

<code>function alert_go($msg,$url){    echo "<script language="javascript" type="text/javascript">";    echo "window.location.href='$url'";    echo "alert('$msg')";    echo "</script>";}$username=$_POST['username'];$pass=$_POST['pass'];$pass2=$_POST['pass2'];$email=$_POST['email'];if(!filled_out($_POST)){    echo "信息不全，不能录入！";    exit;}if(!valid_email($email)){    echo "邮箱格式不正确，请重新检查!";    exit;}if($pass != $pass2){    echo "两次密码不一致,请重新输入";    exit;}if((strlen($pass)16)){    echo "密码长度不正确，请重新输入";    exit;}//echo "注册成功"; @ $db=new mysqli('localhost','root','020310','demo'); if(mysqli_connect_errno()) {    echo "数据库连接错误，请检查后重新连接";    exit; } $query="insert into user(username,password,email) values(?,?,?)"; $stmt=$db->prepare($query); $stmt->bind_param('sss',$username,$pass,$email); $ss=$stmt->execute(); if($ss) {    alert_go('注册成功!','http://baidu.com');    //header('Location: http://localhost/login/login.html'); }else{    alert_go('注册失败！','http://baidu.com'); } 为什么最后跳转不到百度页面啊</code>