Can I use one class type to declare and define variables in another class?

Can I use one class type to declare and define variables in another class? I tried it myself. no, what should I do?

Reply to discussion (solution)

Is that what the landlord said?
Class aa {
Public $ name;
}

Class bb {
Function testaa (aa $ ){
$ A-> age = 333;
}
}

$ Aa = new aa ();
$ Bb = new bb ();

$ Bb-> testaa ($ aa );

Echo $ aa-> age;

Although the code is simple, it is a bit complicated to pass this value. I have no mental preparation at all.

What does "aa $ a" mean? I am a newbie. I have never seen this syntax. where do I look at this?

You can paste your code to see it.
What do people's code mean?

Oh, the factory model. I just saw it before .....

I have extends inherited that class, and it is easy to work.