I see a lot of people go off into the deep end with all kinds of complicated databases and transformation tools. Maybe this works for very large projects with lots op people working on them.
My experience is:
If you want to be able to translate texts in a reasonably efficient manner, you should keep small texts for multiple languages together and separate them for large texts. For instance, I use a lot of scripts that generate forms. So I start every page with an array that contains words and phrases:
if ($lang == "nl")
$texts = array("name"=>"Naam", "age"=>"Leeftijd");
else
$texts = array("name"=>"Name", "age"=>"Age");
(I include a header that figures out the user's language by the http accept language, user and site domains (none of which are foolproof) or authentication/cookie data for registered users.)
Translating this is very simple: copy the array definition and change the phrases. You don't want to use a database for this, because you need to be able to look at the from and to languages at the same time. For large texts I include html files. Translating them isn't much of a problem, keeping several versions up to date is harder.
Don't forget that many users speak more than one language. For instance, many users I talk to in Dutch on my site want to see links to content in both Dutch and English, so when they sign up they can choose between Dutch, English, Dutch + English and English + Dutch.
