On the Zend Developer Zone today there's a new tutorial they've posted looking at adding multi-language support to your applications with the help of the Zend_Translate component of the Zend Framework. It makes it simple to swap between sets of language data without much effort on your part.
If you're a Web developer building an application for global consumption, it's important for you to build in a framework for multi-language support right from the start. Fortunately, there are a number of ready-made components that can help with this task. This article will introduce you to one such component, Zend_Translate, and demonstrate how you can use it to add multi-language support to your PHP application.
There's no "magic bullet" here that'll do the translation for you, but he shows you how to set up the data for the different languages, either in PHP arrays or in translation files, that the Zend_Translate component knows how to use. He also mentions the component's ability to scan a directory tree for language files an detect the language based on a naming convention. He also mentions the "gettext" tool that you can use to generate language files based on a standard GNU format that can be used cross-language with several different tools.
There's lots of other handy bits in the tutorial so I suggest reading if you're thinking about any kind of translation for your site.