bp_document_update_folder_modified_date( int $folder_id )

function bp_document_update_folder_modified_date( $folder_id = 0 ) {

	global $wpdb, $bp;

	if ( 0 === $folder_id ) {
		return false;
	}

	$q = $wpdb->query( $wpdb->prepare( "UPDATE {$bp->document->table_name_folder} SET date_modified = %s WHERE id = %d", bp_core_current_time(), $folder_id ) ); // db call ok; no-cache ok;

	if ( false === $q ) {
		return false;
	}

	return $folder_id;
}