写了个简单的注册页面,可填完表单,点击提交,页面没有反应解决方法

写了个简单的注册页面,可填完表单,点击提交,页面没有反应
填完表单,点击提交,页面没有反应
代码:
<html>
<head>
<title>register page</title>
</head>
<body>
<?php
if(!empty($_POST['submit']))
{
  $username=$_POST['username'];
  $password=$_POST['password'];
  $verify_ps=$_POST['verify_ps'];
  $email=$_POST['email'];
  $qq=$_POST['qq'];
}
if(!isset($_POST['username'],$_POST['password'],$_POST['verify_ps'],$_POST['email']))
{
?>
<form>
  <fieldset>
  <legend>user information:</legend>
  <legend>user acount:</legend>
  <p>
  <label>username:</label>
  <input name="username" type="text">
  </p>
  <p>
  <label>password:</label>
  <input name="password" type="password">
  </p>
  <p>
  <label>verify password:</label>
  <input name="verify_ps" type="password">
  </p> 
 <legend>contact information:</legend>
  <p>
  <label>e-mail:</label>
  <input name="email" type="text">
  </p>
  <p>
  <label>qq:</label>
  <input name="qq" type="text">
  </p>
  <input name="submit" type="submit" value="sign in" class="tj">
  </fieldset>
</form>
<?php
}
else{
  $mysql=new mysqli('localhost','webuser','123456');
if(!$mysql)
{  
echo "can't connect to db.";
exit;
}
$select=$mysql->select_db('user',$mysql);//设定与链接标识符(这里是$mysql)相关联的当前激活数据库
if(empty($select))
{
die("can't select to db.");
}
$s_username="select name='".$username."'from picuser";
$s_email="select e_mail='".$email."'from picuser";
$name_result=$mysql->query($s_username);
$email_result=$mysql->query($s_email);
$n_row=$name_result->fetch_row();
$e_row=$email_result->fetch_row();
if($n_row||$e_row){
echo "this username has been registered." ;  
exit;
}
$insert_user="insert into picuser(name,password,e_mail,qq) values ('".$username."','".$password."','".$email."','".$qq."')";
$insert_result=$mysql->query($insert_user); 
if($insert_result)
{
die('insert data is fail.');
}else{
echo "you has registered successful!";
}
}
?>
</body>
</html>

------解决方案--------------------
表单写规范点啦。
<form method="post" action="">
------解决方案--------------------
把表单跟PHP分开写不是好点吗?用P标签 ?用teble是不是有意义一点呢!
------解决方案--------------------
有点长呵呵,将html和php分离点比较好