Ever wondered how you can modify the way the default Comment block outputs the list of comments? In this article I’m going to show you how to override theme_comment_block() in order allow you to display these comments however you want.

If you look into comment.module (look but don't touch), you’ll notice that the Comment block content is given by the theme_comment_block() function:

function comment_block_view($delta = '') {
  if (user_access('access comments')) {
    $block['subject'] = t('Recent comments');
    $block['content'] = theme('comment_block');
    return $block;
  }
}

So this is what you need to override. To do that, like usual go ahead and copy the original from its API page:

function theme_comment_block() {
  $items = array();
  $number = variable_get('comment_block_count', 10);
  foreach (comment_get_recent($number) as $comment) {
    $items[] = l($comment->subject, 'comment/' . $comment->cid, array('fragment' => 'comment-' . $comment->cid)) . '&nbsp;<span>' . t('@time ago', array('@time' => format_interval(REQUEST_TIME - $comment->changed))) . '</span>';
  }
  if ($items) {
    return theme('item_list', array('items' => $items));
  }
  else {
    return t('No comments available.');
  }
}

...and then make the modifications you want. Don’t forget to change theme in the function name with the name of your module or theme. As an example below, I will override this function in my demo theme in order to add an html entity (») before each comment subject:

function demo_comment_block() {
  $items = array();
  $number = variable_get('comment_block_count', 10);
  foreach (comment_get_recent($number) as $comment) {
    $items[] = l('&raquo; ' . $comment->subject, 'comment/' . $comment->cid, array('fragment' => 'comment-' . $comment->cid, 'html' => true)) . '&nbsp;<span><em>' . t('@time ago', array('@time' => format_interval(REQUEST_TIME - $comment->changed))) . '</em></span>';
  }
  if ($items) {
    return theme('item_list', array('items' => $items));
  }
  else {
    return t('No comments available.');
  }
}

So let’s break this theme function down a bit. As you can see, it first retrieves the n recent comments on the site (n being the number you set in the block configuration form). Then, iterating through that array of comments, another array ($items) is filled with the comment subjects passed through the l() function plus the comment's timestamp. If you don’t know the l() function construct, check it out on its API page, it is very cool and useful.

Now, I did 2 things for my purpose. I added my html entity right before the comment subject and passed to the l() function the html attribute setting it to TRUE. This makes sure my html entity is parsed as html and not plain text (more information on this in the l() function documentation).

And that is pretty much it. I mean, you can do a lot more than this. I just gave you a short example. For questions or clarifications, just drop a comment below.