Attention: You need some experience for use this optional code.

/* Add like and unlike to array */
Find $mods = array and add like, unlike to that array

/* Button Like and Unlike with checking */
$check_like = mysql_result(mysql_query("select count(*) from forum_like where user_id = '".$user_id."' and id = '".$res['id']."' "), 0);
if($user_id && $user_id != $res['user_id']) {
if($check_like == 0) echo '<a href="/forum/index.php?id='.$res['id'].'&amp;act=like#'.$res['id'].'">Like</a>';
elseif($check_like == 1) echo '<a href="/forum/index.php?id='.$res['id'].'&amp;act=unlike#'.$res['id'].'">Unlike</a>';
}

/* Array user who like post */
$user_like = array();
$export_user_like = mysql_query("SELECT `user_id` FROM `forum_like` WHERE `id` = '".$res['id']."'");
while($show_like = mysql_fetch_array($export_user_like)) {
if($user_id != $show_like['user_id'])
$user_like[] = '<a href="/users/profile.php?user='.$show_like['user_id'].'">'.nick($show_like['user_id']).'</a>';
else
$user_like[] = 'You';
}

/* Show user who like post */
if(!empty($user_like)) echo implode(', ',$user_like).' like this post.';

/* Export count of likes */
find `forum`.* and add `users`.`likes` (you need to do this 2 times)

/* Show count of likes that user have */
if($res['likes'] != 0) echo 'Like: '.$res['likes'];

// Attention: add this to div of each post for active hidden id
id="'.$res['id'].'"