Thanks a lot, Elef, for your detailed response. I will explain you my purpose so that you might have an idea what could be the best for me.
I know a little about machine translation stuff but it's not what I need for my project. I am working on the text classification which is using a bag-of-words approach. So my translation task is very easy. Just word-by-word since any text will be split into words anyway. And all EU languages into English only. Which also simplifies the task.
I think using a third party translation servers is an overhead to me and it is not very reliable especially when it comes to massive queries. So my guess is that I should use some simple word-to-word translation procedure on my server.