BCC multiple email addresses, including the site admin email address, on all Event Tickets' RSVP ticket emails so they get a copy of it too

functions.php

<?php
/**
 * BCC multiple email addresses, including the site admin email address, on all Event Tickets' RSVP ticket emails so they get a copy of it too
 *
 * Updated 2018-01-18 for Event Tickets 4.5.2+
 * HOWEVER, this has been tested and we think there might be an issue with
 * the version of PHPMailer (what wp_mail() uses) included with WordPress, which
 * is why BCCs are not working.
 * Therefore, you can use this other snippet for how to initiate a new, separate
 * email message to the Organizer (but it could be customized to go to someone
 * else, such as the site admin):
 * @link https://gist.github.com/niconerd/16770b84adb6156aaa77948bf208bacb
 *
 * From https://gist.github.com/cliffordp/c4fb2ea8fb5ca44973ff06e6facc9742
 * A fork of https://gist.github.com/cliffordp/4f06f95dbff364242cf54a3b5271b182
 * For https://theeventscalendar.com/support/forums/topic/event-tickets-free-not-plus-rsvp-notifications/#post-1272819
 *
 * @link https://developer.wordpress.org/reference/functions/wp_mail/#comment-349
 */
function cliff_et_rsvp_bcc_admin_and_more_ticket( $email_headers, $event_id, $order_id ) {
	// did not work? $event_organizer_emails = tribe_get_organizer_email( $event_id );
	$bccs = array(
		get_option( 'admin_email' ),
		// the site admin email, probably do not want to edit this line
		'someone@example.com',
		// edit or delete this line
		'another@anywhere.com',
		// edit or delete this line, and even add another if you want
	);

	if ( is_array( $email_headers )) { // should always be true but just to be safe
		// add each BCC email if it's a valid email address
		foreach ( $bccs as $bcc ) {
			$bcc = sanitize_email( $bcc );

			if ( is_email( $bcc ) ) {
				$email_headers[] = sprintf( 'Bcc: %s', $bcc );
			}
		}
	}

	return $email_headers;
}

add_filter( 'tribe_rsvp_email_headers', 'cliff_et_rsvp_bcc_admin_and_more_ticket', 10, 3 );