Live Notifications UML Class Diagram

php symfony notifications uml entity-relationship

Just a few observations:

The two abstract classes seem to be superfluous since you use them only in one context.
The hasconnection from User should go to UserEndNotification rather than the abstract class (which I recommend to drop anyway).
I'd make NotificationType an <<enumeration>>
rather than using an owns relation I would use an association class between User and Event and add an isOwner and isSubscriber property.

CodeHunter