Extracting a column from the database and further data processing (RedBeanPHP). How to implement?

Question

PHP

Good evening!
Task : run a php script by cron (every 10-15 minutes), which will connect to the database, retrieve values ​​from a certain column, then compare these values ​​with the current time and if in some "cell" the difference with the current time is significant - we perform certain actions.
What is it for? I have a WebSocket server (Workerman) running on php. Clients are connected to this server. Periodically, I exchange messages with them (like ping-pong, if the client answers me, I write down the current time to the database for him). If the client disconnects purposefully (not a connection break) - I will see it. But if the connection is closed due to a break, I can't see it. Such feature of Workerman.
I need to monitor the connection of each client, so I want to check his "heartbeat" in this way.
How can this be implemented?