refatorado.php

<?php
class Saveimg
{
    private $save;

    public function __construct(Save $save)
    {
        $this-save = $save;
    }

    public function save($file)
    {
        $this-save->save($file);
    }
}

interface Save
{
    public function save($file);
}

class Original implements Save
{
    public function save($file)
    {
        //lógica
    }
}

class Thumb implements Save
{
    public function save($file)
    {
        //lógica
    }
}

class Medium implements Save
{
    public function save($file)
    {
        //lógica
    }
}