Show comments from multiple post IDs in comment template

Question

This may sound like an unusual request but I am try to display comments from several related posts in a single comment template.

For example I have several posts on the same topic (IDs 253, 724, 798) and I want all comments from these posts to appear next in a continuous thread. So if I am viewing post ID 724 I can also see the comments from posts 253 and 798.

Can I pass multiple post IDs to the comments template to achieve this does this require a custom query before or after the comments template to show all the comments in a merged thread?

Answer 1

you can get comments from each post by its id with

$comments253 = get_comments('post_id=253');
$comments724 = get_comments('post_id=724');
$comments798 = get_comments('post_id=798');

then merge ( array-merge ) and sort the array by date ( comment->comment_date being the key to the date value) if you want. then just

 foreach($comments as $comment) :
      echo($comment->comment_author . '<br />' . $comment->comment_content);
 endforeach;

This is all very manual, and you might want to automatize the process, but that's probably an different matter.

Answer 2

Getting the comments for multiple posts is rather simple: Just replace comment_post_ID = YOUR_POST_ID with an IN() function.

function wpse_59687_multiple_comment_post_id_query_filter( $query )
{
    $post_ids = array ( 149, 188, 151 );
    if ( FALSE === strpos( $query, 'comment_post_ID = ' ) )
    {
        return $query; // not the query we want to filter
    }

    remove_filter( 'query', 'wpse_59687_multiple_comment_post_id_query_filter' );

    $replacement = 'comment_post_ID IN(' . implode( ',', $post_ids ) . ')';
    return preg_replace( '~comment_post_ID = \d+~', $replacement, $query );
}

Now you call this function just before you call comments_template():

add_filter( 'query', 'wpse_59687_multiple_comment_post_id_query_filter' );

What’s more difficult:

• get_comments_number() is wrong. You have to filter its value too.
• Replies to a comment from another post are redirected to the URL of the other post, not the page where the commenter has written the comment. Fixing that will be not so trivial …