function bbp_update_forum_last_active_id( $forum_id = 0, $active_id = 0 ) {

	$forum_id = bbp_get_forum_id( $forum_id );

	// Define local variable(s)
	$children_last_active = 0;

	// Do some calculation if not manually set
	if ( empty( $active_id ) ) {

		// Loop through children and get the last active ID
		$children = bbp_forum_query_subforum_ids( $forum_id );
		if ( ! empty( $children ) ) {
			foreach ( $children as $child ) {
				$children_last_active = bbp_update_forum_last_active_id( $child, $active_id );
			}
		}

		// Get topic IDs and only accept larger IDs
		$topic_ids = bbp_forum_query_topic_ids( $forum_id );
		if ( ! empty( $topic_ids ) ) {

			// Make sure ID is larger
			$active_id = bbp_forum_query_last_reply_id( $forum_id, $topic_ids );
			$active_id = $active_id > max( $topic_ids )
				? $active_id
				: max( $topic_ids );

		// Forum has no topics
		} else {
			$active_id = 0;
		}
	}

	// Cast as integer in case of empty or string
	$active_id            = (int) $active_id;
	$children_last_active = (int) $children_last_active;

	// If child forums have higher ID, use that instead
	if ( ! empty( $children ) && ( $children_last_active > $active_id ) ) {
		$active_id = $children_last_active;
	}

	update_post_meta( $forum_id, '_bbp_last_active_id', $active_id );

	// Filter & return
	return (int) apply_filters( 'bbp_update_forum_last_active_id', $active_id, $forum_id );
}