WP_REST_Users_Controller::get_items PHP Method

    public function get_items($request)
    {
        // Retrieve the list of registered collection query parameters.
        $registered = $this->get_collection_params();
        /*
         * This array defines mappings between public API query parameters whose
         * values are accepted as-passed, and their internal WP_Query parameter
         * name equivalents (some are the same). Only values which are also
         * present in $registered will be set.
         */
        $parameter_mappings = array('exclude' => 'exclude', 'include' => 'include', 'order' => 'order', 'per_page' => 'number', 'search' => 'search', 'roles' => 'role__in');
        $prepared_args = array();
        /*
         * For each known parameter which is both registered and present in the request,
         * set the parameter's value on the query $prepared_args.
         */
        foreach ($parameter_mappings as $api_param => $wp_param) {
            if (isset($registered[$api_param], $request[$api_param])) {
                $prepared_args[$wp_param] = $request[$api_param];
            }
        }
        if (isset($registered['offset']) && !empty($request['offset'])) {
            $prepared_args['offset'] = $request['offset'];
        } else {
            $prepared_args['offset'] = ($request['page'] - 1) * $prepared_args['number'];
        }
        if (isset($registered['orderby'])) {
            $orderby_possibles = array('id' => 'ID', 'include' => 'include', 'name' => 'display_name', 'registered_date' => 'registered', 'slug' => 'user_nicename', 'email' => 'user_email', 'url' => 'user_url');
            $prepared_args['orderby'] = $orderby_possibles[$request['orderby']];
        }
        if (!current_user_can('list_users')) {
            $prepared_args['has_published_posts'] = true;
        }
        if (!empty($prepared_args['search'])) {
            $prepared_args['search'] = '*' . $prepared_args['search'] . '*';
        }
        if (isset($registered['slug']) && !empty($request['slug'])) {
            $prepared_args['search'] = $request['slug'];
            $prepared_args['search_columns'] = array('user_nicename');
        }
        /**
         * Filters WP_User_Query arguments when querying users via the REST API.
         *
         * @link https://developer.wordpress.org/reference/classes/wp_user_query/
         *
         * @since 4.7.0
         *
         * @param array           $prepared_args Array of arguments for WP_User_Query.
         * @param WP_REST_Request $request       The current request.
         */
        $prepared_args = apply_filters('rest_user_query', $prepared_args, $request);
        $query = new WP_User_Query($prepared_args);
        $users = array();
        foreach ($query->results as $user) {
            $data = $this->prepare_item_for_response($user, $request);
            $users[] = $this->prepare_response_for_collection($data);
        }
        $response = rest_ensure_response($users);
        // Store pagination values for headers then unset for count query.
        $per_page = (int) $prepared_args['number'];
        $page = ceil((int) $prepared_args['offset'] / $per_page + 1);
        $prepared_args['fields'] = 'ID';
        $total_users = $query->get_total();
        if ($total_users < 1) {
            // Out-of-bounds, run the query again without LIMIT for total count.
            unset($prepared_args['number'], $prepared_args['offset']);
            $count_query = new WP_User_Query($prepared_args);
            $total_users = $count_query->get_total();
        }
        $response->header('X-WP-Total', (int) $total_users);
        $max_pages = ceil($total_users / $per_page);
        $response->header('X-WP-TotalPages', (int) $max_pages);
        $base = add_query_arg($request->get_query_params(), rest_url(sprintf('%s/%s', $this->namespace, $this->rest_base)));
        if ($page > 1) {
            $prev_page = $page - 1;
            if ($prev_page > $max_pages) {
                $prev_page = $max_pages;
            }
            $prev_link = add_query_arg('page', $prev_page, $base);
            $response->link_header('prev', $prev_link);
        }
        if ($max_pages > $page) {
            $next_page = $page + 1;
            $next_link = add_query_arg('page', $next_page, $base);
            $response->link_header('next', $next_link);
        }
        return $response;
    }