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Date: Wed, 11 Jun 2025 17:34:48 +0200
To: Rob Landers <rob@bottled.codes>
Cc: Volker Dusch <volker@tideways-gmbh.com>, php internals
 <internals@lists.php.net>
Subject: Re: [PHP-DEV] [VOTE] Clone with v2
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 <8f4bdf65-6237-45c8-92a9-82347dfb85a7@app.fastmail.com>
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

Am 2025-06-08 21:15, schrieb Rob Landers:
> So, it seems like this can only be used for things that can already be 
> cloned?

Yes. It's an extension of the existing cloning functionality.

> Things which are directly trying to block an identical clone, but would 
> otherwise be fine with a clone that changes the value (e.g. value 
> objects) aren’t allowed to use this new feature?
> To me, that feels like an oversight in the design.

Trying to enforce “singleton” objects to be able to `===` compare them 
already requires you to take care of quite a number of things (e.g. 
making the constructor private, disallowing serialization, …) and 
cloning is no different in that regard.

Nevertheless you can make `__clone()` private (which means that cloning 
is only allowed from within the class, no Exception necessary) and then:

     private function __clone() { }

     public function withFoo($foo) {
         if ($this->foo === $foo) {
             return $this;
         }

         return clone($this, ['foo' => $foo]);
     }

To make sure you are only creating a clone when actually changing 
anything.

Best regards
Tim Düsterhus