comment-suppressor.php

<?php

/**
 * Plugin Name: Comment Suppressor
 * Description: Hide comments for anonymous and “Subscriber” users.
 * Version: 1.0.1
 * Author: Samuel Coleman <samuel@seenet.ca>
 * License: WTFPLv2
 */

/**
 * Suppress comments for a post if the user is anonymous, or if the user only
 * belongs to the “Subscriber” role.
 *
 * @param array $comments the comments for the post
 * @param int $post_id the ID of the post
 */
function suppress_comments($comments, $post_id)
{
    if (!is_user_logged_in())
    {
        return [];
    }

    $user = wp_get_current_user();
    $roles = $user->roles;

    /* The user should never have zero roles, but if they do, they're
     * _definitely_ not allowed to see comments. Otherwise, users may have
     * multiple roles; e.g., “Contributor” stacks on top of “Subscriber”, so we
     * only want to suppress comments for users who have _only_ the
     * “Subscriber” role. */
    if (count($roles) === 0
        || (count($roles) === 1 && in_array('subscriber', $roles)))
    {
        return [];
    }

    return $comments;
}

add_filter('comments_array', 'suppress_comments', 0, 2);