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Date: Tue, 4 Feb 2020 10:01:11 -0500
Message-ID: <CAPKYkKwWCbeyQTUV6C6xOff4Q7ObYXzHTrnJCL-6LHy6Hk2+Qg@mail.gmail.com>
To: Marco Pivetta <ocramius@gmail.com>
Cc: "Aimeos | Norbert Sendetzky" <norbert@aimeos.com>, Benjamin Eberlei <kontakt@beberlei.de>, 
	Steven Wade <stevenwadejr@gmail.com>, PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC - discussion] __toArray()
From: chasepeeler@gmail.com (Chase Peeler)

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On Tue, Feb 4, 2020 at 9:23 AM Marco Pivetta <ocramius@gmail.com> wrote:

> On Tue, Feb 4, 2020, 14:50 Aimeos | Norbert Sendetzky <norbert@aimeos.com>
> wrote:
>
> > Am 04.02.20 um 14:43 schrieb Marco Pivetta:
> > >> I think we can't classify it as BC break, because no existing code
> > >> implements __toArray at the moment, and hence it will not fail when
> this
> > >> feature is introduced and code gets upgraded to newer versions.
> > >
> > > It is a BC break because it changes the semantic of `(array) $object`:
> > the
> > > operation is no longer stable between two versions of the language.
> >
> > It wouldn't be a BC breaking change if `(array) $object` works like
> > before when __toArray() isn't implemented by an object. As nobody should
> > have implemented __toArray() because it's a reserved name for magic
> > methods, we should be fine.
> >
>
> The operation in question, when seen by its signature, is:
>
> (array) :: object FieldTypes -> Map String FieldTypes
>
> The proposed RFC changes this to (pardon the weird union type: my type-fu
> is not that advanced):
>
> (array) :: (FieldTypes|IO ToArrayTypes a) => object a -> Map String a
>
> This changes the return type of a very much pure function (even makes it
> non-pure: fun), and is a very, very, very clear BC break.
>
> >
>
I think we all know that I'm very big on avoiding BC breaks. I personally
don't see this as a BC break, though. At least not one with PHP.

Right now, behavior when casting things to an array is like so:
(array)$scalar ==> [$scalar]
(array)$array ==> $array
(array)$object ==> [$prop1=>$val1, $prop2=>$val2, ...]

So, assuming that right now I have the code:
$x = new SomeThirdPartyArrayLikeObject();
//stuff
$y = (array)$x;
//$y ==> [$prop1=>$val1, $prop2 => $val2, ...]

In a future version, in order to make that library more array-like, the
following is added:
public function __toArray(){
   return [$this];
}

Based on that, I'd argue that the BC break is with the library, not PHP. If
the __toArray function is not implemented on that class, then nothing
changes. The only way you'd get BC breaks with PHP itself is if core (and,
arguably extension) classes started behaving differently when cast to an
array.

I'm personally in favor of anything that is going to allow us to create
array-like objects that can be treated like arrays. I personally hate
having to write:

if(is_object($var)){
  $x = [$var];
} else {
  $x = (array)$var;
}

No, the other question is whether we do it with a magic method, like
__toArray() or an interface. I personally like magic methods, but, in the
end I'm ambivalent on that.

-- 
Chase Peeler
chasepeeler@gmail.com

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