Solution Review: Abstract Classes and Methods

<?php
abstract class User {
    protected $username = '';
    abstract public function stateYourRole();
    public function setUsername($name) {
        $this -> username = $name;
    }
    public function getUsername() {
        return $this -> username; 
    }
}
class Admin extends User {
  public function stateYourRole() {
    return "admin"; 
  }
}
class Viewer extends User {
  public function stateYourRole() {
    return strtolower(__CLASS__); 
  }
}
function test()
{
  $admin1 = new Admin();
  $admin1 -> setUsername("Balthazar"); 
  return $admin1 -> stateYourRole();
}
echo test();
?>