I would just like to point out that while it is possible to register sessions in advance, it is not necessary. Attendees can register sessions on the day. In fact, often an idea for a session comes up, after talking to other attendees at the event. This is one of the key elements of PHP Unconference Europe: The sessions are intended to be a starting point for discussion. The most interesting discussions take place in the breaks between the sessions and fuel the ideas for further sessions.