// get posts
$posts = SelectAllPosts();

// loop through posts
foreach($post as $p) {

    // print post title
    print $p['title'];

    // get all comments for current post
    $comments = SelectCommentsForPost($p);

    // loop through comments
    foreach($comment as $c) {
        // print comment title and message
        print $c['title']
        print $c['message'];
    }
}