bbp_update_forum_topic_count_hidden( int $forum_id, int $topic_count )

function bbp_update_forum_topic_count_hidden( $forum_id = 0, $topic_count = 0 ) {
	global $wpdb;

	// If topic_id was passed as $forum_id, then get its forum
	if ( bbp_is_topic( $forum_id ) ) {
		$topic_id = bbp_get_topic_id( $forum_id );
		$forum_id = bbp_get_topic_forum_id( $topic_id );

	// $forum_id is not a topic_id, so validate and proceed
	} else {
		$forum_id = bbp_get_forum_id( $forum_id );
	}

	// Can't update what isn't there
	if ( !empty( $forum_id ) ) {

		// Get topics of forum
		if ( empty( $topic_count ) ) {
			$post_status = "'" . implode( "','", array( bbp_get_trash_status_id(), bbp_get_spam_status_id() ) ) . "'";
			$topic_count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(ID) FROM {$wpdb->posts} WHERE post_parent = %d AND post_status IN ( {$post_status} ) AND post_type = '%s';", $forum_id, bbp_get_topic_post_type() ) );
		}

		// Update the count
		update_post_meta( $forum_id, '_bbp_topic_count_hidden', (int) $topic_count );
	}

	return (int) apply_filters( 'bbp_update_forum_topic_count_hidden', (int) $topic_count, $forum_id );
}