PHP工厂模式计算面积与周长

<?php
interface InterfaceShape
{
    function getArea();
    function getCircumference();
}

/**
 * 矩形
 */
class Rectangle implements InterfaceShape
{
    private $width;
    private $height;
    public function __construct($width,$height){
        $this->width=$width;
        $this->height=$height;
    }
    public function getArea(){
        return $this->width*$this->height;
    }
    public function getCircumference(){
        return 2*$this->width+2*$this->height;
    }
}
/**
 * 圆
 */
class circle implements InterfaceShape{
    private $redius;
    public function __construct($redius){
        $this->redius = $redius;
    }
    public function getArea(){
        return M_PI*pow($this->redius,2);
    }
    public function getCircumference(){
        return M*PI*2*$this->redius;
    }
}
class FactoryShape{//func_get_arg(索引)返回当前函数指定索引的参数值，返回string格式；
    static public function create(){
        switch (func_num_args()) {
            case 1:
                return new circle(func_get_arg(0));
            case 2:
                return new Rectangle(func_get_arg(0),func_get_arg(1));
            default:
                break;
        }
    }
}
$rect = FactoryShape::create(5,5);
var_dump($rect);
echo "<br>";
$circle = FactoryShape::create(4);
var_dump($circle);
?>