Increase quantity when adding same Option - php

Question

I have managed to implement OOP of Cart Basket
An Item contain 1 or more options.
If I add same OptionID again then the number of quantity should increase rather than creating another Option Object. How can that be done?
If I add same ItemID again, it should refuse to create another Item object.
Also is my OOP is good?
class Cart {
public $item = array();
public function addItem($id) {
$item = new Item();
$item->setItem($id);
$this->item[] = $item;
return $item;
}
}
class Item {
private $id = array();
private $option = array();
public function setItem($id) {
$this->id = $id;
return $this;
}
public function addOption($id) {
$option = new Option();
$option->setOption($id);
$this->option[] = $option;
}
}
class Option {
private $quantity;
private $id;
public function setOption($id) {
$this->quantity = 1;
$this->id = $id;
return $this;
}
}
$cart = new Cart();
//ItemID 10
$item = $cart->addItem(10);
//OptionID
$item->addOption(11);
$item->addOption(22);
$item->addOption(22); //should increase quantity
//It should not create another object because we already have Item Object of ItemID10
$item = $cart->addItem(10);
$Shop = $cart;
echo "<pre>";
print_r($Shop);
echo "</pre>";

Answer 1

If you can have only one item with the unique id in the cart - then rewrite the addItem() method like this:
public function addItem($id) {
$result = false;
if (empty($this->item[$id])) {
$item = new Item();
$item->setItem($id);
$this->item[$id] = $item;
$result = $item;
}
return $result;
}
The same is with addOption() method:
public function addOption($id) {
if (empty($this->option[$id])) {
$option = new Option();
$option->setOption($id);
$this->option[$id] = $option;
}
else {
$this->option[$id]->setQuantity($this->option[$id]->getQuantity() + 1);
}
}
And of course you should implement setQuantity() and getQuantity() methods in Option class.
Hope this helps.

Answer 2

Partialy rewrote the code and tested:
<?php
class Cart {
public $items = array();
public function addItem($id) {
if(array_key_exists($id, $this->items)){
$item = $this->items[$id];
}else{
$item = new Item($id);
$this->items[$id] = &$item;
}
return $item;
}
}
class Item {
private $id;
private $options = array();
public function __construct($id) {
$this->id = $id;
return $this;
}
public function addOption($id) {
if(array_key_exists($id, $this->options)){
$this->options[$id]->addQuantity();
}else{
$option = new Option($id);
$this->options[$id] = $option;
}
}
}
class Option {
private $quantity;
private $id;
public function __construct($id) {
$this->quantity = 1;
$this->id = $id;
return $this;
}
public function addQuantity()
{
$this->quantity++;
}
}
$cart = new Cart();
//ItemID 10
$item = $cart->addItem(10);
//OptionID
$item->addOption(11);
$item->addOption(22);
$item->addOption(22); //should increase quantity
//It should not create another object because we already have Item Object of ItemID10
$item = $cart->addItem(10);
$Shop = $cart;
echo "<pre>";
print_r($Shop);
echo "</pre>";
?>