<?php
class Alpha{
function one(){
    $object1->three();
    return 1;
    }

function two(){
    return 2;
    }
}
class Beta{
function three(){
    return 3;
    }
function four(){
    return 4;
    }
}

$object0 = new Alpha();
$object1 = new Beta();

$object1->one(); ??

?>