How to store Strings&Text in Webfrontends for multiple languages

Whats the best practice for saving Strings in Webdeveloping?

Simple textfile including the strings for different languages?

Saving everything in a database and create a big JS File from that? Or request every String from the Database using ajax?

The biggest requirement is that it has to be usable in PHP/JS-TemplateFrameworks/JS.

How do you save them?