Nested lazy ghost fails with clone

[mkroeders]

Description

In a library I do reflection of objects and want to support nested references. So use lazy ghost/proxies for creating nested objects to prevent endless loop and with a combination of caching to prevent redoing the same objects multiple times. However it breaks when using clone inside the factory method. Tested it with the newLazyGhost and newLazyProxy.

Not sure if it is supported behavior, but looking at the rfc it only mentions nesting in combination with throwing exceptions.

The following code:

<?php
class Bar {
    public function __construct(
        public Bar $bar,
        public int $x,
    ) {}

    public function with(): self
    {
        return clone $this;
    }
}

class Fiz {
    public mixed $cache = null;

    public function foo(int $i)
    {
        if (!$this->cache) {
            $this->cache = $this->factor($i);
        }

        if ($i <= 1) {
            return $this->cache->with();
        }

        return $this->cache;
    }

    public function factor(int $i): object
    {
        $reflector = new ReflectionClass(Bar::class);

        return $reflector->newLazyGhost(
            function (Bar $bar) use ($i) {
                $bar->__construct($this->foo($i + 1), 2);
            },
        );
    }
}

$fiz = new Fiz();

$f = $fiz->foo(0);
var_dump($f->bar->bar->x);

https://3v4l.org/lYpu1

Resulted in this output:

PHP Fatal error:  Uncaught Error: Typed property Bar::$bar must not be accessed before initialization

But I expected this output instead:

int(2)

PHP Version

PHP 8.4.3 (cli) (built: Jan 15 2025 01:03:17) (NTS)
Copyright (c) The PHP Group
Built by Homebrew
Zend Engine v4.4.3, Copyright (c) Zend Technologies
    with Xdebug v3.4.0, Copyright (c) 2002-2024, by Derick Rethans
    with Zend OPcache v8.4.3, Copyright (c), by Zend Technologies

Operating System

Mac OS

[arnaud-lb]

Thank you for your report.

This looks like expected behavior.

The error happens when accessing property bar on a non-lazy object whose bar property is uninitialized. This object (lets call it B) was created by cloning another non-lazy object (A) whose bar property was also uninitialized.

What is happening in details:

• $fiz->foo(0) creates a lazy object A, and clones it immediately
• The documentation describes the behavior of cloning a lazy object as follows:

  • Cloning a lazy object triggers its initialization before the clone is created, resulting in an initialized object (https://www.php.net/manual/en/language.oop5.lazy-objects.php#language.oop5.lazy-objects.cloning)

• Therefore A is initialized.
• As per the documentation, the first step of initialization is to mark the object as non-lazy (with the consequence that any operation on the object will not call the initializer again): https://www.php.net/manual/en/language.oop5.lazy-objects.php#language.oop5.lazy-objects.initialization-sequence
• Before setting A::$bar, the initializer clones A again (via $this->foo($i + 1)) (lets call the clone B). Therefore B::$bar is not set.
• Later we access B::$bar, which results in the error Uncaught Error: Typed property Bar::$bar must not be accessed before initialization.

Here is a simpler example:

class Bar {
    public function __construct(public Bar $bar) {}
}

$A = (new ReflectionClass(Bar::class))->newLazyGhost(function (Bar $A) {
    printf("Initializing A\n");
    $B = clone $A;
    $A->__construct($B);
});

$C = clone $A;

echo "\$A->bar:\n";
var_dump($A->bar);
echo "\$A->bar->bar:\n";
var_dump($A->bar->bar);

Output:

Initializing A
$A->bar:
object(Bar)#1 (0) {
  ["bar"]=>
  uninitialized(Bar)
}
$A->bar->bar:

Fatal error: Uncaught Error: Typed property Bar::$bar must not be accessed before initialization in test.php:18