PHP OOP

By Korvin Szanto

Why use OOP?

• Adds types to values
• Organizes common functions
• Give state to services

Classes

Objects

<?php

class Shirt
{

    // Properties
    public $color;
    public $size;

    // Functions
    public function getString()
    {
        $size = $this->size;
        $color = $this->color;
        return "{$size} {$color} Shirt"
    }

    // Constructor
    public function __construct($color, $size)
    {
        $this->color = $color;
        $this->size = $size;
    }

}

<?php

function output_shirt(Shirt $shirt) {
    echo $shirt->getString();
}

// Create a new Shirt
$shirt = new Shirt('Blue', 'Large');

// Output the shirt: "Large Blue Shirt"
output_shirt($shirt);

Extending Classes

<?php

class Sweater extends Shirt
{

    public $material;

    public function getString()
    {
        $color = $this->color;
        $size = $this->size;
        $material = $this->material;
        return "{$size} {$color} {$material} Sweater";
    }

    public function __construct($color, $size, $material)
    {
        $this->material = $material;
        
        // Call Shirt's constructor with the color and the size
        parent::__construct($color, $size);
    }

}

<?php

function output_shirt(Shirt $shirt) {
    echo $shirt->getString();
}

// Create a new Sweater
$shirt = new Sweater('Blue', 'Large', 'Wool');

// Output the shirt: "Large Blue Wool Sweater"
output_shirt($shirt);

Interfaces

<?php

interface ClothingInterface
{

    public function getString();

}

<?php

class ClothingOutputter
{

    public function outputClothing(ClothingInterface $clothing)
    {
        echo $clothing->getString();
    }

}

<?php

class LargeBlueJeans implements ClothingInterface
{

    public function getString()
    {
        return "Large Blue Jeans";
    }

}

<?php

interface StoreItemInterface
{

    /**
     * Get the price of a store item
     * @return float The price, 10.0 for $10.00, 9.58 for $9.58
     */
    public function getPrice();

}

<?php

class LargeBlueJeans implements ClothingInterface, StoreItemInterface
{

    public function getString()
    {
        return "Large Blue Jeans";
    }

    /**
     * Get the price of a store item
     *
     * @return float The price in dollars and cents, Ex: 10.0 for $10.00, 9.58 for $9.58
     */
    public function getPrice()
    {
        return 12.0;
    }

}

<?php

interface TaxExemptStoreItemInterface
{
}

<?php

interface CartInterface
{

    /**
     * Get the total price of this cart
     * @return float 
     */
    public function getTotal();

    /**
     * Get the items in this cart
     * @return StoreItemInterface[]
     */
    public function getItems();

    /**
     * Get the items in this cart
     * @return bool
     */
    public function addItem(StoreItemInterface $store_item);

}

Traits

<?php

trait TotalingStoreItemListTrait
{

    /**
     * @return StoreItemInterface[]
     */
    abstract public function getItems();

    /**
     * Get the total price of this item list
     */
    public function getTotal()
    {
        $items = $this->getItems();

        $total = 0;
        foreach ($items as $item) {
            $total += $this->getPriceForItem($item);
        }

        return $total;
    }

    /**
     * Get the price of an item
     */
    protected function getPriceForItem(StoreItemInterface $item)
    {
        return $item->getPrice();
    }

}

<?php

trait TaxableTotalingStoreItemListTrait
{

    use TotalingStoreItemListTrait;

    protected $flat_tax_rate = 1.0;

    /**
     * Get the price of an item
     */
    protected function getPriceForItem(StoreItemInterface $item)
    {
        $price = $item->getPrice();

        if (!$item instanceof TaxExemptStoreItemInterface) {
            $price *= $this->flat_tax_rate;
        }

        return $price;
    }

}

<?php

class Cart implements CartInterface
{

    use TaxableTotalingStoreItemListTrait;

    protected $items = [];

    protected $flat_tax_rate = 1.5;

    /**
     * Get the items in this cart
     * @return StoreItemInterface[]
     */
    public function getItems()
    {
        return $this->items;
    }

    /**
     * Get the items in this cart
     * @return bool
     */
    public function addItem(StoreItemInterface $store_item)
    {
        $this->items[] = $store_item;
    }

}

<?php

trait StoreItemListTrait
{

    protected $store_item_list_items = [];

    /**
     * Get the items in this cart
     * @return StoreItemInterface[]
     */
    public function getItems()
    {
        return $this->store_item_list_items;
    }

    /**
     * Get the items in this cart
     * @return bool
     */
    public function addItem(StoreItemInterface $store_item)
    {
        $this->store_item_list_items[] = $store_item;
    }

}

<?php

class Cart implements CartInterface
{

    use StoreItemListTrait, TaxableTotalingStoreItemListTrait;

    protected $flat_tax_rate = 1.5;

}

Namespaces

<?php

namespace Acme\Depot\Store\Item\List;

use Acme\Depot\Store\Item\TaxExemptInterface;

trait TaxableTotalingTrait
{

    use TotalingTrait;

    protected $flat_tax_rate;

    public function setTaxRate($rate)
    {
        $this->flat_tax_rate = $rate;
    }

    /**
     * Get the price of an item
     */
    protected function getPriceForItem(StoreItemInterface $item)
    {
        if ($item instanceof TaxExemptInterface) {
            return $item->getPrice();
        } else {
            return $item->getPrice * $this->flat_tax_rate;
        }
        return $item->getPrice();
    }

}

<?php
namespace Acme\Depot\Store;

use Acme\Depot\Store\Item\List\TaxTotalingTrait;
use Acme\Depot\Store\Item\List\ListTrait;

// Use vendor cart interface
use Vendor\Store\Cart\CartInterface;

class Cart implements CartInterface
{

    use ListTrait, TaxableTotalingTrait;

    protected $flat_tax_rate = 1.5;

}

Thanks!