关于对象克隆

<?php
class Car {
    public $name = 'car';
    
    public function __clone() {
        $obj = new Car();
        //$obj->name = $this->name;

        $obj->name='test';

    }
}
$a = new Car();
$a->name = 'new car';
$b = clone $a;
echo $b->name;

?>

我的问题是$b = clone $a;此时$b是指由$a调用__clone生成的对象还是？如果是那么echo $b->name;应该打印的值是‘test’,而实际结果确是 new car