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Date: Fri, 15 Nov 2013 08:29:38 -0600
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To: Chris London <me@chrislondon.co>
Cc: "internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Proposal: Type Casting User Classes
From: leverton@gmail.com (Matthew Leverton)

On Thu, Nov 14, 2013 at 12:39 PM, Chris London <me@chrislondon.co> wrote:
> Hey everyone,
>
> I want to get a feel for something I would like to implement into PHP core.
>  I would like to be able to cast objects to my own class types.  Similar to
> already available PHP syntax:
>
> $foo = (string) $bar;
>
I've thought about this feature before in the context of PHP because I
do think it would be useful, but I'm not sure if there's really a way
to implement it that is any better than userland solutions. Your
proposed __cast() call means that every object needs to know about
every object which breaks down when multiple projects are involved.
(Sure, it solves some cases nicely.)

And I wouldn't be a fan of implicit conversions like:

function foo (Foo $foo) { }
foo(new Bar());

Assuming Bar does not descend from Foo, I wouldn't want a cast to Foo
to be implicitly performed even if Bar had an appropriate "cast"
method.

So ultimately, I don't really see how a PHP solution is any better
than just using home made explicit casts:

$bar = cast_foo_to_bar($foo);

or

$bar = $foo->castToBar();

So I think the idea has merit, but I don't know that there's a good
way to implement it.

--
Matthew Leverton