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Date: Mon, 16 Jan 2017 10:17:42 +0100
Message-ID: <CADyq6sJpQNDfyn_DpWY+YLRpxe3Fu47WEDzBO-v3hiQq1T-bAg@mail.gmail.com>
To: =?UTF-8?Q?Micha=C5=82_Brzuchalski?= <michal@brzuchalski.com>
Cc: Wes <netmo.php@gmail.com>, PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a11423eec20e850054632a914
Subject: Re: [PHP-DEV] Unsetting declared fields
From: ocramius@gmail.com (Marco Pivetta)

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On Mon, Jan 16, 2017 at 9:49 AM, Micha=C5=82 Brzuchalski <michal@brzuchalsk=
i.com>
wrote:

> Hi Marco,
>
> 2017-01-16 0:27 GMT+01:00 Marco Pivetta <ocramius@gmail.com>:
>
>> Hi Wes,
>>
>> This has been discussed before, and it's currently used to intercept
>> access
>> to properties. Since we don't have property accessors (sigh), the code
>> (simplified version) would look like following:
>>
>> class Foo
>> {
>>     public $bar =3D 'baz';
>> }
>>
>> class FooInterceptor extends Foo
>> {
>>     private $wrapped;
>>     public function __construct(Foo $wrapped)
>>     {
>>         $this->wrapped =3D $wrapped;
>>         unset($this->bar);
>>     }
>>     public function __get(string $name)
>>     {
>>         var_dump('reading ' . $name);
>>         return $this->wrapped->$name;
>>     }
>> }
>>
>> $foo =3D new FooInterceptor(new Foo);
>>
>> var_dump($foo->bar);
>>
>> You can see a working example at https://3v4l.org/UtugD
>
>
> There is one more thing might be confusing - reflection tells there still
> exists bar property after unset while it's realy not.
> For example https://3v4l.org/NAg1l
>
> $class =3D new ReflectionClass(FooInterceptor::class);
> $property =3D $class->getProperty('bar');
> var_dump($property); // still exists while actually being unset may cause
> errors
>
> I'm sticking to extending class without magic _get method implemented.
>
>
>>
>>
>> This behavior is protected from regressions since PHP 5.4, but has been
>> working since 5.0:
>> https://github.com/php/php-src/blob/cd2b462a2742c79256668d47
>> 36644e34573c33d9/tests/classes/unset_properties.phpt
>>
>> We can most probably get rid of this weird behavior once property
>> accessors
>> are in the language.
>>
>> Greets,
>>
>> Marco Pivetta
>>
>> http://twitter.com/Ocramius
>>
>> http://ocramius.github.com/
>>
>> On Mon, Jan 16, 2017 at 12:20 AM, Wes <netmo.php@gmail.com> wrote:
>>
>> > Hello elephpants.
>> >
>> > Currently PHP allows explicitly declared fields (eg public $foo =3D 10=
;)
>> to
>> > be removed entirely through unset (eg unset($obj->foo)).
>> >
>> > Now that isn't really an issue as properties in php are currently
>> untyped
>> > and therefore nullable; at worst you would get a notice. But it would
>> > become an issue with typed fields... that might get a second chance
>> sooner
>> > or later.
>> >
>> > But regardless of that, it looks very strange to me that this is allow=
ed
>> > for fields that are explicitly declared. I think unset() should set th=
e
>> > field to null if it's declared in the class, and remove the field
>> > altogether only if it was defined dynamically.
>> >
>> > On the other hand, this is just one of many ways of hacking php that
>> just
>> > exist and we accept / don't care because we have faith in other people
>> not
>> > doing nasty stuff with our code. This might sound ironic it is actuall=
y
>> not
>> > :P
>> >
>> > However, I am curious: what you think about this? Should PHP do
>> something
>> > in regard? Should this continue to work like it does now? Why do you
>> feel
>> > it should do the one or the other?
>> >
>>
>
Hi Micha=C5=82,

Reflection will also trigger `__get` in this scenario, which is expected
and was also reverted multiple times in "fixes" that worked around or
forgot to call the property access guards.

class Foo
{
    public $bar =3D 'baz';
}

class FooInterceptor extends Foo
{
    private $wrapped;
    public function __construct(Foo $wrapped)
    {
        $this->wrapped =3D $wrapped;
        unset($this->bar);
    }
    public function __get(string $name)
    {
        var_dump('reading ' . $name);
        return $this->wrapped->$name;
    }
}

$foo =3D new FooInterceptor(new Foo);

$reflectionFooBar =3D new \ReflectionProperty(Foo::class, 'bar');

var_dump($reflectionFooBar->getValue($foo));

See https://3v4l.org/6JtWT for a working example.

You can see
https://github.com/Ocramius/ProxyManager/tree/cce5477857504997baf3168974b8f=
1283516a686/tests/language-feature-scripts
for

As I already mentioned, this hack is currently necessary to make property
access interception transparent, which is common for most AOP-oriented
code. We need an alternate approach to make this happen, before such a
feature can be dropped.

Marco Pivetta

http://twitter.com/Ocramius

http://ocramius.github.com/

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