WordPress plugin to limit editing of pages and their children to certain user roles.

role-limiter.php

<?php

/**
 * Plugin Name:     Role-Based Page Editor Limitations
 * Description:     This plugin restricts editing capabilities of specific pages to certain user roles. It dynamically creates roles if they don't exist and assigns them editor capabilities. It then checks if a user with a specific role is trying to edit a page that they're not assigned to, and if so, it removes their editing capabilities for that page. Edit the $role_page_map array to specify which roles can edit which pages.
 * Version:         1
 * Author:          Greg R.
 */

/* For example you want to make it so that some peolple at your company can edit /subpage/ and all the children under that page, so you can create a user role that restricts them to jus that section of the site. */


global $role_page_map;
// user role as key and page path as value
// note that the page and any children (and childrens children etc) of the page will be editable by the user with the role
$role_page_map = array(
    'subpage_editor' => 'subpage'
);

// Loop over the role-page map
foreach ($role_page_map as $role => $page_path) {
    // If the role doesn't exist
    if (!get_role($role)) {
        // Get the capabilities of the editor role
        $editor_capabilities = get_role('editor')->capabilities;

        // Create a friendly name for the role
        $friendly_name = ucwords(str_replace('_', ' ', $role));

        // Add the new role with the capabilities of the editor role
        add_role($role, $friendly_name, $editor_capabilities);
    }
}
function role_based_edit_map_meta_cap($caps, $cap, $user_id, $args) {
    global $role_page_map;

    // If we're checking the 'edit_post' or 'edit_page' capability
    if ('edit_post' === $cap || 'edit_page' === $cap) {
        // Get the post
        $post = get_post($args[0]);

        // Get the user
        $user = get_userdata($user_id);

        // Check each role in the role-page map
        foreach ($role_page_map as $role => $page_path) {
            // If the user has the current role
            if (in_array($role, $user->roles)) {
                // Get the ID of the page for this role
                $page_id = get_page_by_path($page_path)->ID;

                // Check if the post is a descendant of the page
                $is_descendant = false;
                $parent_id = $post->post_parent;
                while ($parent_id != 0) {
                    if ($parent_id == $page_id) {
                        $is_descendant = true;
                        break;
                    }
                    $parent_post = get_post($parent_id);
                    $parent_id = $parent_post->post_parent;
                }

                // If the post is not the page or a descendant of the page
                if ($post->ID != $page_id && !$is_descendant) {
                    // Remove the 'edit_post' or 'edit_page' capability
                    $caps[] = 'do_not_allow';
                }
            }
        }
    }

    return $caps;
}
add_filter('map_meta_cap', 'role_based_edit_map_meta_cap', 10, 4);

?>