Solution Review: Inheritance

<?php
class User {
    protected $username;
    public function setUsername($name) {
        $this -> username = $name;
    }
}
class Admin extends User {
    public function expressYourRole() {
        return strtolower(__CLASS__); 
    }
    
    public function sayHello() {
        return "Hello admin, " . $this -> username; 
    }
}
function test(){
    $admin1 = new Admin();
    $admin1 -> setUsername("Balthazar"); 
    return $admin1 -> sayHello();
}
echo test();
?>