What we need to do is to have the client save the event on the server when it is created.
In this chapter, we'll use PHP sessions to save the data for the sake of simplicity.
Sessions are chunks of data, which are kept on the server side and are related to the cookie or
PHPSESSID parameter that the client uses to access that session. We will use sessions in these examples because they do not need as much setup as databases.
For your own projects, you should adapt the PHP side in order to connect to a database instead.
If you are using this chapter to create a full application, you will obviously want to use something more permanent than sessions, in which case the PHP code should be adapted such that all references to sessions ...