<?php

abstract class Shape
{
	abstract function Draw();
}

class Square extends Shape
{
	function Draw()
	{
		echo "Square";
	}
}

class Circle extends Shape
{
	function Draw()
	{
		echo "Circle";
	}
}

abstract class DynamicFactory
{
	protected static $types = array();

	public static function Register($type, $class)
	{
		self::$types[$type]=$class;
	}

	public static function IsRegistered($type)
	{
		if (isset(self::$types[$type]))
			return true;
		else
			return false;
	}

	public static function Create($type)
	{
		if (isset(self::$types[$type]) && 
		class_exists(self::$types[$type]))
			return new self::$types[$type];
		else
			return null;
	}
}

class ShapeFactory extends DynamicFactory { }

ShapeFactory::Register("square","Square");
ShapeFactory::Register("circle","Circle");

$a_square = ShapeFactory::Create("square");
$a_circle = ShapeFactory::Create("circle");

$a_square->Draw();
echo "\n";
$a_circle->Draw();
echo "\n";
	
?>