I think my website got hacked

Strange thing is in your config you have this:

PHP Code:

$config['sess_cookie_name'] = 'ci_session'; 


Meaning the session filenames should start with ci_session follow by the session_id. And that is also not the case.
Are you the only one working on this project? And if you can, check the current online version to a version that was working before this error started

Hey Martin ,
yes I'm the only one person who is working on this project. actually it was the online version that I've post.
i think my website was working for 15 days and then that happened! But my tech support from the server said: I've update your php version from 5.4 to 5.5 so the problem solved!