<?php

class B
{
    public $id = 123;
}

class C
{
    private $values = [1, 2, 3];
    private $ident = 'abc';
}

class A
{
    private $b;
    public $c;
    private $age = 42;
    private $name = 'Foo';

    public function __construct(B $b)
    {
        $this->b = $b;
    }
}

class D
{
    public $name = 'Test';
    private $age = 42;
}

$a = new A(new B());
$a->c = new C();

$d = new D();
//print serialize($d);

function serialized(stdClass $std, string $class): string
{
    return sprintf(
        'O:%d:"%s"%s',
        strlen($class),
        $class,
        strstr(strstr(serialize($std), '"'), ':')
    );
}

function cast(stdClass $std, string $class, array $properties = [])
{
    foreach($std as $key => $prop) {
        if ($prop instanceof stdClass) {
            $std->{$key} = cast($prop, $properties[$key]);
        }
    }

    $serialized = preg_replace(
        '/^O:\d+:"[^"]++"/',
        'O:' . strlen($class) . ':"' . $class . '"',
        serialize($std)
    );

    if ($class === A::class) {
        print_r($serialized);
        exit;
    }

    return unserialize($serialized);
}

var_dump($d);
var_dump($a);

print '====' . PHP_EOL;

$std1 = json_decode('{"name":"Test"}');
var_dump(cast($std1, D::class));
$std2 = json_decode('{"b":{"id":123},"c":{"values":[1,2,3],"ident":"abc"},"age":42,"name":"Foo"}');
var_dump(cast($std2, A::class, ['b' => B::class, 'c' => C::class]));