Restrict login wrong 3 times

cek_login.php

 
<?php

include "config/koneksi.php";

function antiinjection($data){

 $filter_sql = mysql_real_escape_string(stripslashes(strip_tags(
htmlspecialchars($data,ENT_QUOTES))));

  return $filter_sql;

}

$username = antiinjection($_POST['username']);

$pass     = antiinjection(md5($_POST['password']));

if (!ctype_alnum($username) OR !ctype_alnum($pass)){

  echo "<script type=text/javascript>

        alert('Script Login');

        window.location.href='login.php'



        </script>";

  //header('location:index.php');

}else{

$login=mysql_query("SELECT * FROM users WHERE username='$username' AND password='$pass' AND blokir='N'");

$ketemu=mysql_num_rows($login);

$r=mysql_fetch_array($login);



 if ($ketemu > 0){

            mysql_query("UPDATE users SET batas_login = 0 where username='$username'");

            session_start();

            session_register("namauser");

            session_register("namalengkap");

            session_register("passuser");

            session_register("leveluser");



              $_SESSION[namauser]     = $r[username];

              $_SESSION[namalengkap]  = $r[nama_lengkap];

              $_SESSION[passuser]     = $r[password];

              $_SESSION[leveluser]    = $r[level];

             

        header('location:home.php');

  } else{

       

mysql_query("UPDATE users SET batas_login = batas_login + 1 where username='$username'");

              

 $a=mysql_fetch_array(mysql_query("SELECT batas_login from users where username = '$username'"));

        $b=$a['batas_login'];

        if($b > 2){

        mysql_query("UPDATE users SET blokir = 'Y' where username='$username'");

        echo "<script type=text/javascript>

              alert('Username $username Telah Di Blokir, Silahkan Hubungi Administrator');

           window.location.href='register.php'

              </script>";

  }  else{

        echo "<script type=text/javascript>

              alert('Username Atau Password Tidak Benar Anda, Sudah $b Kali Mencoba');

              window.location.href='index.php'

              </script>";

           }

        }

    }

?>