Mine

<?php
	class Person {
		var $name;

		function Person ( $name ) {
			$this->name = $name;
		}

		function open (&$object) {
			$object->open = true;
		}
	}

	class Door {
		var $open = false;

		function status () {
			return $this->open ? 'open' : 'closed';
		}
	}

	$person = new Person ('cshobe');
	$door = new Door ();
	
	echo 'Door is '.$door->status ().'<br/>';
	echo $person->name.' is trying to open $door<br/>';
	$person->open ($door);
	echo 'Door is '.$door->status ().'<br/>';
?>