PHP Class类问题

<?phpclass Car{ var $color; function Car($color="green") { $this->color = $color; } function what_color() { return $this->color; }}function print_vars($obj) { foreach (get_object_vars($obj) as $prop => $val) { echo "\t$prop = $val\n"; }}$herbie = new Car("white");print_vars($herbie);?>

PHP新人一枚，今天在W3C看到PHP对象类型，看了半天不解为什么结果是输出 color = white能否帮我每行都注释下