Factory

Factory.php

<?php

class Factory
{
    public function create()
    {
        $this->context->create();   
    }

    public function setContext($context)
    {
        $this->context = $context;
    }
}

SlotsInterface {
    public function create();
}

class OW implements SlotsInterface
{
    public function create()
    {
        echo 'create two slots' . PHP_EOL;
    }
}

class AR implements SlotsInterface
{
    public function create()
    {
        echo 'Create four slots' . PHP_EOL;
    }
}

//Usage

$f = new Factory();
$f->setContext(new AR());
$f->create(); // Four slots created
$f->setContext(new OW());
$f->create(); // two slots created