alone之后的两个对象为什么===返回还是flase

<?php

class Car {

    public $name = 'car';

    public function __clone() {

        $obj = new Car();

        $obj->name = $this->name;

    }

}

$a = new Car();

$a->name = 'new car';

$b = clone $a;

if ($a == $b) echo '==';   //true

if ($a === $b) echo '==='; //false