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To: internals@lists.php.net,Rasmus Schultz <rasmus@mindplay.dk>,PHP internals <internals@lists.php.net>
Message-ID: <876C54BA-B07F-4468-8709-36C495D04311@gmail.com>
Subject: Re: [PHP-DEV] scalar type-casting
From: rowan.collins@gmail.com (Rowan Collins)

On 9 April 2017 10:30:02 BST, Rasmus Schultz <rasmus@mindplay=2Edk> wrote:
>Example:
>
>class Foo { public function __toString() { return "foo"; } }
>function append_to(string &$str) { $str =2E=3D "_bar"; }
>$foo =3D new Foo();
>append_to($foo);
>var_dump($foo); // string(7) "foo_bar"
>
>In this example, the caller's instance of Foo gets wiped out and
>replaced
>by a string=20

While this looks surprising in the form you've written it, it should only =
really be a surprise to the function author, not the caller=2E If the calle=
r sees only the signature, then the function can do *literally anything* to=
 their passed by reference variable=2E The caller is giving full control an=
d "ownership" of that variable, and shouldn't make any assumptions about wh=
at it will look like when it comes back=2E

For example, you don't even need PHP7 to do this:

class Foo { public function __toString() { return "foo"; } }
function append_to(&$str) { $str =3D (string)$str =2E "_bar"; }
$foo =3D new Foo();
append_to($foo);
var_dump($foo); // string(7) "foo_bar"

I don't think it's any more unreasonable for a reference parameter to chan=
ge type in the parameter handling of your example function (with strict_typ=
es off) than inside the body of my example function=2E Of course, by settin=
g strict_types=3D1, the caller can change the implicit cast to an implicit =
assertion, and get an error in your example; it won't save them from my exa=
mple, though=2E

Regards,

--=20
Rowan Collins
[IMSoP]