Add options to block bookings 2, 3 or 4 days in advance in the Restaurant Reservations plugin.

custom-late-booking-for-rtb.php

<?php
/**
 * Plugin Name: Custom Late Bookings Options for Restaurant Reservations
 * Plugin URI: http://themeofthecrop.com
 * Description: Add options to block bookings 2, 3 or 4 days in advance in the Restaurant Reservations plugin.
 * Version: 0.0.1
 * Author: Theme of the Crop
 * Author URI: http://themeofthecrop.com
 * License:     GNU General Public License v2.0 or later
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU
 * General Public License as published by the Free Software Foundation; either version 2 of the License,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write
 * to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */
if ( ! defined( 'ABSPATH' ) )
        exit;

if ( !function_exists( 'rtb_custom_late_bookings_options' ) ) {
add_filter( 'rtb_settings_page', 'rtb_custom_late_bookings_options' );
function rtb_custom_late_bookings_options( $sap ) {

        $sap->pages['rtb-settings']->sections['rtb-schedule']->settings['late-bookings']->options['2880'] = __( 'At least 2 days in advance', 'restaurant-reservations' );
        $sap->pages['rtb-settings']->sections['rtb-schedule']->settings['late-bookings']->options['4320'] = __( 'At least 3 days in advance', 'restaurant-reservations' );
        $sap->pages['rtb-settings']->sections['rtb-schedule']->settings['late-bookings']->options['5760'] = __( 'At least 4 days in advance', 'restaurant-reservations' );

        return $sap;
}
} // endif;