How to tell is this is a user's first visit?

[eluser]Yorick Peterse[/eluser]
[quote author="FlashChilli" date="1246832223"]Oh, I was hoping I wouldn't have to do that as the table could get pretty huge. It doesn't have to be perfect as I only want to count the number of unique visitors and total up how many are using certain browsers, so it's not too bad if some people are counted a few times. To be honest, I'd rather modify the sessions class than use a database but I'm not sure how to.[/quote]

You can't use the session class as it will expire eventually, unless you would set the expiration time to 1 year (31 536 000 seconds) or something like that.