PHP Method Chaining

<?php
/*
php method chaining is a technic which we can use for make your program more small. for this you have to return all the chained method all the class for this you have to use return $this; 
*/
class Calculator{
	private $num1;
	private $num2;
	private $result;

	public function Set($num1, $num2){
		$this->num1 = $num1;
		$this->num2 = $num2;
		return $this;
	}

	public function Sum(){
		$this->result = $this->num1 + $this->num2;
		return $this;
	}

	public function Sub(){
		$this->result = $this->num1 - $this->num2;
		return $this;
	}

	public function Result(){
		return $this->result;
	}
}
?>
<h1>PHP Method Chaining Example</h1>
<?php
	$cal = new Calculator();
	echo 'The result is : ';
	echo $cal->Set(20, 10)->Sum()->Result();
?>