itemshop.php

<?php
require_once "./simpleitemfactory.php";

class ItemShop {
  private $factory;

  public function __construct(SimpleItemFactory $factory) {
    $this->factory = $factory;
  }

  public function order_item($type) {
    $item = $this->factory->create_item($type);
    return $item;
  }
}

main.php

<?php
require_once "./simpleitemfactory.php";
require_once "./itemshop.php";

$item = (new ItemShop(new SimpleItemFactory()))->order_item("sword");
var_dump($item);
//=>object(SwordItem)#3 (0) {
//=>}

shoesitem.php

<?php
class ShoesItem {
}

simpleitemfactory.php

<?php
require_once "./sworditem.php";
require_once "./shoesitem.php";

class SimpleItemFactory {
  public function create_item($type) {
    $item = null;
    if ($type === "sword") {
      $item = new SwordItem();
    }
    elseif ($type === "shoes") {
      $item = new ShoesItem();
    }
    return $item;
  }
}

sworditem.php

<?php
class SwordItem {
}