integrate template engine in a custom developed php app

I have an existing web based application which sells events tickets online. it also has producers module which allows producer registration, event listing, selling tickets etc. customer can purchase tickets for the listed events, paypal integrated. all the above features are functional and working perfectly fine. I need 2 main things done. TinyButStrong template engine integration and MultiLanguage support integration to the above app. You don't need to translate the application, but just simple PHP file based languages and I will add languages myself later. I need best prices for a long term relation and quick turn around. Thanks