<?php
    if(isset($_POST['ok']))
    {
     if($_POST['username'] == NULL)
     {
      echo "Please enter your username<br />";
     }
     else
     {
      $u=$_POST['username'];
     }
     if($_POST['password'] == NULL)
     {
      echo "Please enter your password<br />";
     }
     else
     {
      $p=$_POST['password'];
     }
     if($u && $p)
     {
      $conn=mysql_connect("localhost","root","123456") or die("can't connect this database");
      mysql_select_db("project",$conn);
      $sql="select * from tbluser where username='".$u."' and password='".$p."'";
      $query=mysql_query($sql);
      if(mysql_num_rows($query) == 0)
      {
       echo "Username or password is not correct, please try again";
      }
      else
      {
       $row=mysql_fetch_array($query);
       session_start();
       session_register("userid");
       session_register("level");
       $_SESSION['userid'] = $row[id];
       $_SESSION['level'] = $row[level];

      }
     }
    }
    ?>
    <form action=test.php method=post>
    Username: <input type=text name=username size=25 /><br />
    Password: <input type=password name=password size=25 /><br />
    <input type=submit name=ok value="Dang Nhap" />
    </form>