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To: "'Ryan Pallas'" <derokorian@gmail.com>,
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Date: Tue, 14 Jul 2015 00:56:10 +0200
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Subject: RE: [PHP-DEV] PHP7 and types
From: francois@php.net (=?UTF-8?Q?Fran=C3=A7ois_Laupretre?=)

> De : Ryan Pallas [mailto:derokorian@gmail.com]
>=20
> With all the new typing and strict mode in PHP7, I'm wondering if =
there is
> any planned support for typing of properties in a future version. IE
> something like:
>=20
> class Foo {}
> class Bar {
>    public Foo $foo;
>=20
>    public function __construct(Foo $foo) {
>        $this->foo =3D $foo;
>    }
> }
>=20
> This seems really useful to me. If its not something that was =
considered
> before I can try to write up an RFC for this, however I'm not sure if =
this
> was already considered and denied. Any feedback would be greatly
> appreciated.

Hi,

I proposed this as an addition to scalar type hinting when we were =
discussing the STH RFC some months ago. Zeev and Dmitry, like Rasmus =
today, thought it was probably not possible to implement it without huge =
changes to the engine. After thinking more about it, I think they're =
absolutely right. What you want to implement is not an additional =
compile-time check, it's attaching type hints to object properties. =
That's a runtime check *and* a possible conversion *each* time a =
property is assigned. The problem is that the current engine makes it =
impossible to trap every zval assignments, let alone the question of =
performance. If you look at parameter type hints, argument types are =
checked only once, when they are received by the function. Then, in the =
function body, you can assign any value/type to every received argument, =
that's impossible to check.

Rewriting your example to show the feature has nothing to do with =
compile-time checks :

public function __construct(Foo $foo) {
manage($foo);
$this->foo=3D$foo; /* Compile-time OK, Runtime error */
}

/* In another file, somewhere... */

public function manage(&$obj)
{
...
$obj=3D'bar';
}

Regards

Fran=C3=A7ois