I am setting up a site that will run in many languages.

It will be in php and will use shared code, just including text files in the appropriate langauges.

The use will select the language by chosing a flag which will be displayed at the top of every page.

The site is a .com site

What do I need to do about meta titles and descriptions? I can easily include include translated versions so that when the user selects the (eg French) flag the meta data is all in French. However, is there any point in this? I will probably use mode rewrites so that the French pages have an address www.mysite.com/fr/detail.html, whereas the English will be www.mysite.com/detail.html

Does anyone else have any experience doing this? Any ideas as to whether this should work? Better suggestion? (And not google autotranslate...)

I recomend you buy domains fr etc and create there your multy anguage site. But it just my opinion.

What is the problem to place translated titles and meta also in language files and output them into the page accordingly?

if you have the budget, I recommend multiple domains - one for each language.
another option is just to make a directory or a sub domain for each language.
in each case when you make an update to a script you have to make sure that you update all the other language sites that make any use of that script.
or you can have the entire content + meta load from file according to a parameter received with the page (i.e. yourpage.php?ln=fr).

What is the problem to make all domains to be served by the same server and detect current language according to domain or subdomain name? I mean that it is quite stupid to have separate bundle of scripts for each language domain.