Newbie asks about multi-lingual website strategies

I'm a noob so keep the comments to a noob's level please. I am doing a website and my client wants the bulk of the text to be bilingual (French and English). The last site I did used php and mysql so I am getting comfortable with that technology. Typically I am using a single php file and my menu constantly points to the same file with different id options example "index.php?id=30" and I want to use the same idea to choose a language example "index.php?lang=fr&id=30". Pretty straight forward for many of you folks but before I start reinventing the wheel I wondered if anyone could offer any suggestions. I have a couple of approaches in mind. 1: Session vars, I have never used this but it seems straight forward. Drawbacks? 2: Cookies again not too big a deal, never used cookies either but it doesn't seem to be mystifying however the fact that the user can turn cookies off makes me not want to go this route. 3: Use the mysql database and log each ip address and record the preference and maybe the last time on the site. I am leaning in this direction because I think it is the most robust but will it be slow? First I have to get the ip then I have to check to see if it is in my data base and then get the language preference. It would be great to have a standardized function that I could use on all of my sites. I live in a bilingual country (Canada) so this could be a real selling point for my services. Any any and all comments are welcome, it will be a learning curve no matter which route I take so a little advice on the best direction pros cons would be great. And of course knowing that I will have many many thousands of people on my site (hee hee) which option will perform best once I start accumulating vistors. That's one problem I see with the mysql solution, I think it may start to be slow unless I start purging vistors who have not shown up in a while or limit the number of entries. Thanks, Jeff