How to track multiple instances of the same user (object)

I'm writing an IRC bot in PHP, and I wanted to make a s little more sophisticated then most other bots.

I have the following classes in my application:

Bot - The actual bot class, it handles all of the functionality and commands the bots can get.
Registry - Global settings and variables, passed on to any functioning class so that I don't have to litter the global namespace with variables.
Channel - Defines the channel object, properties: $name, $nicklist, where $name is the channel name and $nicklist is an array of User objects.
User - Defines the user object, properties: $nickname, $fullAddress, where $fullAddress is the user's address in the form of nick!user@host.

So far so good, however, a user may be on multiple channels, and since I don't want to have multiple objects from the same user (as if a user, for instance, changes his nickname, I'll have to update multiple elements instead of just one).

How would I go about this, I was thinking about holding a grand user pool at the base of the Bot class, and pass these references to the channels, but I don't really know how to do that either :P

Can anyone point me in the right direction? I can paste my current code if you'd like (it's rather long so I rather not do it if no one needs it).

Thanks.

Solution

Since the Bot object is the one that needs to do the tracking, have an array of User objects on it, and pass the pointers to those objects (aka $bot->users['name']) to the Channel object.

That way, the same pointer can be passed twice in case the user is already found on the users list.