Strategy.php

<?php

interface IDiscount{

		function calculateDiscount($bill);
	}

	class NoDiscount implements IDiscount{

		public function calculateDiscount($bill){

			return $bill;
		}
	}

	class LowDiscount implements IDiscount{

		public function calculateDiscount($bill){

			return $bill * 0.9;
		}
	}

	class HighDiscount implements IDiscount{

		public function calculateDiscount($bill){

			return $bill * 0.7;
		}
	}	

	class BuyGames{

		private $totalcost = 0;
		public $discountInstance = null;

		public function buyGame($name, $cost){

			echo $name . ": " . $cost ." Euro \r\n";
			$this->totalcost = $this->totalcost + $cost; 
			echo "Total Cost: ". $this->totalcost . " Euro \r\n";

			return $this->totalcost;
		}

		public function discount(IDiscount $discountType){

			$this->discountInstance = $discountType;

			return $this->discountInstance->calculateDiscount($this->totalcost);
		}
	}

	//Client

	$bgames = new BuyGames();

	$bgames->buyGame("Zork", 24);
	$bgames->buyGame("Super Mario", 30);
	$bgames->buyGame("Sonic", 40);

	echo "Total with 30% discount: " . $bgames->discount( new HighDiscount() ) . "\r\n";
	echo "Total with 10% discount: " . $bgames->discount( new LowDiscount() ) . "\r\n";
	echo "Total with no discount: " . $bgames->discount( new NoDiscount() ) . "\r\n";


?>