Как клонировать обьект?

interface IObject{
 	function cloner();
 	// function equals();
}

class Uxxankyun implements IObject{
	// public $a;
	// public $b;
	 public function __construct($a,$b){
		$this->a = $a;
		$this->b = $b;
	}
	public function cloner(){
		
	}
}

$u1 = new Uxxankyun(4,5);
$u2 = $u1->cloner();
$u1->a = 8;
print $u2->a;