Language - How to structure a multilanguage site?

[eluser]predat0r[/eluser]
If I understand you

language/english

site_lang.php // english language lines, $lang['page_title'] = 'Title';

language/spanish

site_lang.php // spanish lang lines, $lang['page_title'] = 'Dirección';

And with form validation, if you have specific files for each language in system/language, then it'll switch to the current language version, but to be hones i didn't try form_validation in my single multilang project