php中传统验证与thinkphp框架

<?php

header("Content-type: text/html; charset=utf-8");

$conn =mysqli_connect("localhost","root","");

if (!$conn){

   echo "<script>alert('连接失败！');history.go(-1);</script>";

  } 

mysqli_select_db($conn,"liuyanban");

mysqli_query($conn,'SET NAMES utf8');

$password=$_POST['password'];

$username=$_POST['username'];

$face="yellow.png";

$result=mysqli_query($conn,"SELECT username from user1 where username = '$username'"); 

$a=mysqli_num_rows($result);

if($a)

{    

   echo "<script language=javascript>alert('用户名已存在！');location.href='reg.html'</script>";

}

else

{   

    $sql = mysqli_query($conn,"INSERT INTO user1(username,password,face)VALUES('1' ,'2','yellow.png')");

   if($sql)

   {

      echo "<script language=javascript>alert('注册成功!');location.href='login.html'</script>";

   }

   else

   {

      echo "<script>alert('注册失败！');location.href='reg.html'</script>";

   }

}

?>