Prevent bookings from being made with @aol.com email addresses.

block-aol-for-rtb.php

<?php
/**
 * Plugin Name: Block AOL bookings for Restaurant Reservations
 * Plugin URI: http://themeofthecrop.com
 * Description: Prevent bookings from being made with @aol.com email addresses.
 * Version: 1.0
 * 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;


/**
 * Check if a reservations's email address includes @aol.com
 */
add_action( 'rtb_validate_booking_submission', 'rtbbaol_block_aol_emails' );
function rtbbaol_block_aol_emails( $booking ) {
	if ( !empty( $booking->email ) && strpos( $booking->email, '@aol.com' ) !== false ) {
		$booking->validation_errors[] = array(
			'field'			=> 'email',
			'post_variable'	=> $_POST['rtb-email'],
			'message'	=> __( 'Bookings from @aol.com are not accepted at this time. Please use a different email address.', 'restaurant-reservations' ),
		);
	}
}