Basic Coffee Decorator.php

<?php

/**
 * Our base Coffee class, which has a cost, array of ingredients,
 * and getters/setters. Note that this class is not extended or 
 * implemented, and decorators don't modify Coffee objects.
 */
class Coffee {
    private $cost;
    private $ingredients = array();

    public function __construct($cost, $ingredients=array('coffee')) {
        $this->cost = $cost;
        if (!is_array($ingredients)) {
            $ingredients = array($ingredients);
        }
        $this->ingredients = $ingredients;
    }

    public function getCost() { return $this->cost; }
    public function getIngredients() { return $this->ingredients; }
}

/**
 * Our base decorator class. In this example, the CoffeeDecorator is
 * not an abstract class, though an alternate approach is to make the decorator
 * abstract and then make each decorator extend it.
 */
class CoffeeDecorator {
    protected $coffee;
    protected $cost;
    protected $ingredients = array();

    public function __construct(Coffee $coffee) {
        $this->coffee = $coffee;
        $this->setCost();
        $this->setIngredients();
    }

    public function setCost() {
        $this->cost = $this->coffee->getCost();
    }
    public function setIngredients() {
        $this->ingredients = $this->coffee->getIngredients();
    }
    public function getCost() { return $this->cost; }
    public function getIngredients() { return $this->ingredients; }
    public function getSortedIngredients() {
        $ingredients = $this->getIngredients();
        $arr = array();
        foreach ($ingredients as $ingredient) {
            $arr[$ingredient] = (array_key_exists($ingredient, $arr) ? $arr[$ingredient] : 0) + 1;
        }
        return $arr;
    }
}

/**
 * Here's our first decorator. Creating a MilkyCoffee will add 
 * milk to the ingredients, as well as a corresponding cost.
 * 
 * Note again that this will not modify the original Coffee class.
 */
class MilkyCoffee extends CoffeeDecorator {
    private $decorator;
    protected $cost = 1;
    protected $ingredients = array('Milk');

    public function __construct(CoffeeDecorator $decorator) {
        $this->decorator = $decorator;
        $this->addMilk();
    }

    public function addMilk() {
        $this->decorator->cost = $this->decorator->getCost() + $this->cost;
        $this->decorator->ingredients = array_merge($this->ingredients, $this->decorator->getIngredients());
    }
}

/**
 * Like this MilkyCoffee decorator, this will add a cost and ingredients.
 */
class FoamyCoffee extends CoffeeDecorator {
    private $decorator;
    protected $cost = .5;
    protected $ingredients = array('Steam', 'Milk');

    public function __construct(CoffeeDecorator $decorator) {
        $this->decorator = $decorator;
        $this->addFoam();
    }

    public function addFoam() {
        $this->decorator->cost = $this->decorator->getCost() + $this->cost;
        $this->decorator->ingredients = array_merge($this->ingredients, $this->decorator->getIngredients());
    }
}

/**
 * Let's make some coffee
 */
function run() {
    $coffee = new Coffee(1);
    $decorator = new CoffeeDecorator($coffee);
    echo "\n-------------\ninitial coffee: ($" . $coffee->getCost() . "):\n    " . json_encode($coffee->getIngredients()) . "\n";

    $milky = new MilkyCoffee($decorator);
    echo "\nmilky coffee ($" . $decorator->getCost() . "):\n     " . json_encode($decorator->getSortedIngredients()) . "\n";

    $foamy = new FoamyCoffee($decorator);
    echo "\nfoamy, milky coffee ($" . $decorator->getCost() . "):\n     " . json_encode($decorator->getSortedIngredients()) . "\n";

    echo "\n(adding foam...)";
    $foamy->addFoam();

    echo "\nsuper foamy, milky coffee: ($" . $decorator->getCost() . "):\n     " . json_encode($decorator->getSortedIngredients()) . "\n";

    echo "\nbase coffee: ($" . $coffee->getCost() . "):\n    " . json_encode($coffee->getIngredients());
    echo "\n-------------\n";
}

run();