Assigning functions

Hi all. I have several classes. Within each class, a new class is  
called. Is there a way to assign a function in a *deeper* class to be  
called in the first class? Example to follow......

<?php
class A {
     function __construct () {
         $this->b = new B ();
         // I want to do the following. This does not work, of course.
         $this->doSomething = $this->b->c->doSomething;
     }
}

class B {
     function __construct () {
         $this->c = new C ();
     }
}

class C {
     function __construct () { }
     function doSomething () { echo "¡Hi!"; }
}

$a = new A ();
// Instead of doing this,
$a->b->c->doSomething();

// I want to do this.
$a->doSomething(); // ¡Hi!
?>

Basically, it's just to shorten the line to access a particular  
function. But, is it possible?!

Thanks,
~Philip