NEW FACEBOOK INVITE ALL CODE
Recently facebook changed its event invite system and in order to invite all your friends there is a new method :
Step 1 : Go to the event page you would like to invite all to (example : https://www.facebook.com/event.php?eid=138431042901754 )
Step 2 : Make sure you click "I'm Attending" and then Click on Invite Friends.
Step 3 : You have to now scroll down on your friends list until you reach the bottom, the new infrastructure facebook implimented only lists a certain # of friends at a time (lamesauce) so you gotta scroll down for a minute or two...