Looking for a translation API

I'm looking for API that can translate and return a given text from any language to english. Something like Facebook's button right below every post text/comment saying Translate.

EXAMPLE!

User published a post with the following content (Spanish):

Hola!

After the translate button is clicked an AJAX call is being prepared sending this text to the API and it returns the english string/large text

Hello!

Any ideas what could help me?