Is there software that you can call from, for example a PHP script, to translate languages?

For example, a user has indicated on his preferences that his native language is Spanish. Is there software that can automatically translate the text on the web page from English to Spanish, and also translate what he types in a text box from Spanish into English before storing it in the database (I realise that it won’t be perfect, and the user will have to realise that, too)?

Likewise, French, German, and Italian? How about Chinese and Japanese, though I gather they’d be even more difficult due to the different character sets.