public static function get_placeholders( $args = [] ): array {
		$tickets = self::get_tickets();
		$order   = self::get_order();
		$default = [
			'{attendee_name}'  => $tickets[0]['purchaser_name'],
			'{attendee_email}' => $tickets[0]['purchaser_email'],
			'{order_number}'   => $order->ID,
			'{order_id}'       => $order->ID,
		];
		return wp_parse_args( $args, $default );
	}