if(isset($_POST['btn-login'])) {
   $email = mysqli_real_escape_string($con,$_POST['email']);
   $pass = mysqli_real_escape_string($con,$_POST['pass']);
   $pass = hash('sha256', $pass);

   $sel_user = "select * from users where userName='$email' AND userPass='$pass'";
   $run_user = mysqli_query($con, $sel_user);
   $check_user = mysqli_num_rows($run_user);

   $row = mysqli_num_rows($run_user);

   if($check_user>0) {
      $_SESSION['user']=$email;
      $_SESSION['rank']=$row['userRank'];

      echo "<script>window.open('/staff','_self')</script>";
   }
   else {
      $ErrTyp = "warning";
      $errMSG = "Username or Password is not valid!";
   }
}