using an instance of a class in another class

[eluser]edhrx[/eluser]
I have two small classes 'message' and 'authenicate'
when I call a function in authenticate eg. isLoggedOn I may need to create an error message from the message class but struggling to code it. I realise I could have made authenticate an extesion of message but the message is really a tiny part of what the authenticate class does


Ed.