next message problem

[Anon]

I am trying to display the next messages in phorum program, but the problem is not all of them displayed one after each other. I have to links one for Previous message and one for next message. Previous message link is working good, but next message link is not displaying one after another, sometime displays an empty message. I am using the following for previous message:

 if ($parent != 0) {
     $prev_id = $id - 1;

echo "<A HREF='add_reply_heading.php3?story_id=$story_id&id=
$parent&view=ynot'>Previous Comment</A>&nbsp;&nbsp;";

and I am using the following for next message:

  if ($id < $num_replies) {
    $next_id = $id + 1;

echo "<A
HREF='add_reply_heading.php3?story_id=$story_id&id=$next_id&view=ynot'>Next
Comment</A>&nbsp;&nbsp;";

any help will be appriciated.