interface int1 {
    // Force Extending class to define these methods
    function getArea();
} 

interface int2 {
    function getPerimeter();
} 

class Circle implements int1, int2 {
    static $PI = 3.1415926536;
    public $radius;
    
    public function __construct($radius) {
        $this->radius = $radius;
    }

    public function getPI() {
        return self::$PI;
    }
    
    public function getArea() {
        return pow($this->radius, 2) * self::$PI;
    }
    
    public function getDiameter() {
        return $this->radius * 2;
    }
    
    public function getPerimeter() {
        return $this->radius * 2 * self::$PI;
    }
}

$circle1 = new Circle(5);
echo "\nPI: " . $circle1->getPI();
echo "\nArea: " . $circle1->getArea();
echo "\nDiameter: " . $circle1->getDiameter();
echo "\nPerimeter: " . $circle1->getPerimeter();