bbp_update_topic_last_active_time( int $topic_id, string $new_time = '' )

function bbp_update_topic_last_active_time( $topic_id = 0, $new_time = '' ) {

	// If it's a reply, then get the parent (topic id)
	if ( bbp_is_reply( $topic_id ) ) {
		$topic_id = bbp_get_reply_topic_id( $topic_id );
	} else {
		$topic_id = bbp_get_topic_id( $topic_id );
	}

	// Check time and use current if empty
	if ( empty( $new_time ) ) {
		$new_time = get_post_field( 'post_date', bbp_get_public_child_last_id( $topic_id, bbp_get_reply_post_type() ) );
	}

	// Update only if published
	if ( !empty( $new_time ) ) {
		update_post_meta( $topic_id, '_bbp_last_active_time', $new_time );
	}

	return apply_filters( 'bbp_update_topic_last_active_time', $new_time, $topic_id );
}