Define an interface which has methods area(), volume(). Define constant PI. Create a class cylinder which implements this interface and calculate area and volume.

<?php
interfaceCyl
        {
function area();
function volume();
        }
class Cylinder implements Cyl
        {
public $PI=3.14;
public $a;
public $r;
public $h;
function __construct($r,$h)
           {
                $this->r=$r;
                $this->h=$h;
           }
function area()
           {
              $this->a=2*$this->PI*($this->h*$this->r);
echo"Area = ".$this->a."<br>";
            }
function volume()
           {
              $this->a=$this->PI*$this->r*$this->r*$this->h;
echo"Volume = ".$this->a."<br>";
            }
        }
       $c=new Cylinder(5,5);
       $c->area();
       $c->volume();
?>