<?php
/**
 * For example, copy the following to "wp-content/mu-plugins/disable-comments.php"
 * to use it as a "must-use plugin" (always-on and before "normals" plugins)
 * https://gist.github.com/mattclements/eab5ef656b2f946c4bfb#gistcomment-3770565
 *
 * Another option:
 * https://keithgreer.dev/wordpress-code-completely-disable-comments-using-functions-php
 */
add_action('admin_init', function () {
    // Redirect any user trying to access comments page
    global $pagenow;

    if ($pagenow === 'edit-comments.php' || $pagenow === 'options-discussion.php') {
        wp_redirect(admin_url());
        exit;
    }

    // Remove comments metabox from dashboard
    remove_meta_box('dashboard_recent_comments', 'dashboard', 'normal');

    // Disable support for comments and trackbacks in post types
    foreach (get_post_types() as $post_type) {
        if (post_type_supports($post_type, 'comments')) {
            remove_post_type_support($post_type, 'comments');
            remove_post_type_support($post_type, 'trackbacks');
        }
    }
});

// Close comments on the front-end
add_filter('comments_open', '__return_false', 20, 2);
add_filter('pings_open', '__return_false', 20, 2);

// Hide existing comments
add_filter('comments_array', '__return_empty_array', 10, 2);

// Remove comments page and option page in menu
add_action('admin_menu', function () {
    remove_menu_page('edit-comments.php');
    remove_submenu_page('options-general.php', 'options-discussion.php');
});

// Remove comments links from admin bar
add_action('init', function () {
    if (is_admin_bar_showing()) {
        remove_action('admin_bar_menu', 'wp_admin_bar_comments_menu', 60);
    }
});