Declare a class in a class

[AxAn]

Is it possible to declare a class in another class?, like:

class FirstClass {
  class SecondClass {
    public $fName;
    public $lName;
    public $age;
  }

  ...some code
}

I seem to remember doing this in PHP4 but I do not get it to work in PHP5.
The reason I want to do it it to send around parameters in a nice way in the class (FirstClass). I could use an array but its nicer to use a class when coding in an IDE since it auto completes the variable names in the class when using an object.

I have been seaching for an answer but not found much, maybe since it's hard to search for "class in class".