$sql =  'SELECT a.login_id,a.username,a.password,b.rank,c.status FROM login as a INNER JOIN login_rank as b ON a.username = b.username INNERJOIN login_stat as c WHERE username="'.$_POST['username'].'" AND password="'.md5($_POST['password']).'"
AND status="ACTIVE"';
$result = mysqli_query($con,$sql);

        if (mysqli_num_rows($result)==1){
    //Login Successful
        session_regenerate_id();
        $member = mysqli_fetch_assoc($result);
        $_SESSION['SESS_MEMBER_ID'] = $member['login_id'];
        $_SESSION['SESS_NAME']      = $member['username'];
        $_SESSION['SESS_RANK']      = $member['rank'];


        if($member['rank']=='administrator'){
        header("location: login_reg.php");
        }

        else if($member['rank']=='student'){
        header("location: student.php");
        }
        else if($member['rank']=='candidate'){
        header("location: candidate.php");
        }

        }

        else{
        $error="Incorrect username or password";

            session_write_close();
        //exit();
        }