Even though many sites use an SQL database for logging, it’s not really the most efficient place to store data from a logging workload. Logs don’t require UPDATE/DELETE or rollback, they’re basically an append-only workload. read more
In other words, put all the logic on the PHP side, just have a MySQL table in which you log any activities using delayed. This would be a function log_activity($session_id, $activity) that you can call from anywhere where there is a loggable activity. read more