Send an error in event fullcalendar



I would like to know how to send an error from change.php.


I'm using it to book items. So, when a reservation is done, the object can't be booked when this reservation takes place.


As people can drag and drop reservations, they can move them where they want and even those belonging to other persons. I made sure that the update of the "event" doesn't register when the dates are wrong or when it's not the owner that is moving it. The problem: after the drop, it's not refreshing automatically, I need to change views or press F5 if I want to see if it has registered or not. In other words, I need to find a way for the page to reload after the drop, so that if there is a problem, the dragged event can return to its original place and an error shows in order to explain why.


I've tried stuff in the change.php file or in fullcalendar.php but nothing worked. I want at least to see if it's possible before disabling the drop and the resize.


Thanks to those who can answer (ps: I've already post that as a comment on the plugin in case of).