Using implements  keyword we can cam implement an interface with a Class. An interface can define method names and arguments, but not the contents of the methods

Define using interface keyword

See the below example on Interface.

<?php
  interface OnlineCalculator {
    public function getArea();
  }
  // Get the Area of a Circle
  class Circle implements OnlineCalculator {
     private $radius;
     public function __construct($radius){
       $this -> radius = $radius;
     }
     public function getArea(){
       return $this -> radius * $this -> radius * pi();
     }
}
 
 
$mycircle = new Circle(3);
echo $mycircle->getArea();
?>