<?php
// Declare a basic shopping card that allows us to
// add products to it, with a member that allows us
// to get the quantity of a product we have added using
// a callback function
class Card
{
	public static $products = Array();


	public static function add($product, $quantity)
	{
		self::$products[$product] = $quantity;
	}

	public static function getQuantity($product)
	{
		$quantity = false;

		array_map(function($value, $key) use($product, &$quantity)
		{
			if($key == $product)
			{
				$quantity = $value;
			}

		},
		array_values(self::$products),
		array_keys(self::$products)
		);

		return($quantity);
	}
}

// Add some items to our card
Card::add('Butter', 1);
Card::add('Milk', 3);
Card::add('Eggs', 6);

// Now get the total 'Eggs' we added
printf('The card contains %d eggs', Card::getQuantity('Eggs'));
?>