Method Chaining with phones

PhoneMethodChaining.php

<?php

class Phone
{
	//Creating private properties
	private $_type; 
	
	private $_os;
	
	public function setType( $type )
	{
		//setting private property equal to the $type variable. 
		$this->_type = $type; 
		
		//returning the private property that has been set to the $type variable. 
		return $this; 
	}
	
	public function setOS( $os )
	{
		//setting private property equal to the $os variable.
		$this->_os = $os;

		//returning the private property that has been set to the $os variable. 
		return $this; 
	}
	
	public function getPhone()
	{
		//returns a sting with the properties being called 
		return 'I have a(n) ' . $this->_type . ' running ' . $this->_os . '.'; 
	}
}

$phone = new Phone(); 

//returns:"I have a(n) HTC One M8 running Android Lollipop."
echo $phone->setType('HTC One M8')->setOS('Android Lollipop')->getPhone();