How to show if a user has read a topic in my forum?

I have created a forum for my website but the only thing I don't have a clue about, is how to show if each user has read each topic or not.

I want each user to know if they have read each topic or not, and for it to be unread for everyone everytime a reply is posted in a topic.

How can i do this using php?

Thanks

 

Keep a record in the database - user number and article number every time someone goes to an article.

 

Sorry, I don't fully understand what you mean

 

Go to Buy, Sell and Trade section then. Seriously, if the given sentence made no sense to you, even if we'll give you a piece of code, you won't know where to put it.

 

I'm not stupid, I did understand what he meant, I just don't want endless inserts on my database everytime someone reads a topic for every topic, I really thought there was a simpler way

 

In order to still have user data after the user is gone, you have to save the data somewhere. A database is the most efficient way to do it.