Use javascript.

Some website refresh will not empty the items in cart.

I know I how to set data to cookies.

But users could easily change that data in client, so cart content could be easily destroyed.

That may send incorrect data to server.

How to avoid this situation?

I found shop site always have some strategy to handle that. They never stored clear information in

cookies. They even stop site if some change in cookie.

Do any term or steps about this?

I don't have much basic knowledge about this, I don't know where I could start this.