<?php

abstract class UserFunctions
{

    function getName()
    {
        return $this->firstname . ' ' . $this->lastname;
    }

}

class User extends UserFunctions
{

    protected $firstname; # Cannot be private!
    protected $lastname;  # Private scope only inside $this class

    function __construct()
    {
        $this->firstname = "Vasilij";
        $this->lastname = "Pupkin";
    }
}

$u = new User();
echo $u->getName(); # Result is 'Vasilij Pupkin' witout scope errors