Check if a reservations's email address includes the @ symbol before accepting.

simple-email-validation-for-rtb.php

<?php
/**
 * Plugin Name: Simple Email Validation for Restaurant Reservations
 * Plugin URI: http://themeofthecrop.com
 * Description: Check if a reservations's email address includes the @ symbol before accepting.
 * 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
 * Requires at least: 4.0
 * Tested up to: 4.01
 *
 * Text Domain: rtbdomain
 * Domain Path: /languages/
 *
 * 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 the @ symbol
 */
if ( !function_exists( 'rtbsev_validate_email' ) ) {
add_action( 'rtb_validate_booking_submission', 'rtbsev_validate_email' );
function rtbsev_validate_email( $booking ) {

	// Don't bother with this check if we already have errors attached
	// to this field.
	$email_errors = array_filter( $booking->validation_errors, 'rtbsev_error_is_email' );
	if ( count( $email_errors ) ) {
		return;
	}

	// Set an error if no @ symbol is found
	if ( !strpos( $booking->email, '@' ) ) {
		$booking->validation_errors[] = array(
			'field'			=> 'email',
			'post_variable'	=> $booking->email,
			'message'	=> __( 'Please enter a valid email address so we can confirm your booking.', 'restaurant-reservations' ),
		);
	}

}
} // endif

/**
 * Check if this validation error is attached to the email field
 */
if ( !function_exists( 'rtbsev_error_is_email' ) ) {
function rtbsev_error_is_email( $error ) {
	return $error['field'] == 'email';
}
} // endif