PDF Tickets extension - Woo attachments filter by attendee

functions.php

<?php

add_filter( 'tribe_tickets_ticket_email_attachments', 'filter_woo_pdf_attachments_by_attendee', 10, 6 );

function filter_woo_pdf_attachments_by_attendee( $attachments, $post_id, $order_id, $tickets, $provider, $args ) {

	$order = wc_get_order( $order_id );

	if ( ! $order ) {
		return $attachments;
	}

	$total_pdf      = count( $attachments );
	$total_attendee = count( $tickets );

	if ( $total_pdf === $total_attendee ) {
		return $attachments;
	}

	if ( $total_attendee > 1 ) {
		return $attachments;
	}

	$is_purchaser = tribe_is_truthy( Tribe__Utils__Array::get_in_any( $tickets, 'is_purchaser' ) );

	if ( $args['send_purchaser_all'] && $is_purchaser ) {
		return $attachments;
	}

	$attendee_id = Tribe__Utils__Array::get_in_any( $tickets, 'attendee_id' );
	$serial      = (int) $attendee_id - $order_id;
	$key_name    = "woo_{$order_id}_{$serial}";

	if ( isset( $attachments[$key_name] ) ) {
		return [ $key_name => $attachments[$key_name] ];
	}

	return $attachments;
}