You are on a server, so you are not running a browser. Cookies are browsers object. In addition they are stored on the system using files. Plus they have an expiration date, after which the cookie is removed.



If you don't want to use files or a database connection, the only remaining space is memory, and the amount of information you can store in it depends on the amount of memory you have. But, by definition, once you stop the server, those information will be lost, unless you save them, (guess where) on a persistent storage (file system or a database).



Why don't you want to use those solutions?

Regards.