如何在运行时通过反射获得受保护属性对象的属性值 - How to get the value of property of protected property object through reflection at runtime?

How to get the value of property of protected property object through reflection at runtime?

我在运行时创建了一个对象。它有一个protected属性，该属性也是在运行时创建的对象。这个属性对象有一个字符串类型的受保护属性，我需要获取它的值。

<?php
class A
{
    // will be set at runtime
    protected $s = 'hello';
}
class B
{
    // will be set at runtime
    protected $a;
    public function setA(A $a)
    {
        $this->a = $a;
    }
}
// for example, somewhere in the library
$a = new A();
$b = new B();
$b->setA($a);
// I have $b returned from some library method call
$r = new ReflectionObject($b);
// How to get 'hello'?

关于反射的文档是相当稀疏的，有人可以帮助我这里吗?

      // for example
    $a = new A();
    $b = new B();
    $b->setA($a);
    $r = new ReflectionClass($b);
    $property = $r->getProperty("a");
    $property->setAccessible(true);
    $a = $property->getValue($b);
    $r = new ReflectionClass($a);
    $property = $r->getProperty("s");
    $property->setAccessible(true);
    $s = $property->getValue($a);

有点棘手，甚至不确定是否需要，但它现在工作了