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Date: Mon, 16 Jan 2017 10:30:50 +0100
Message-ID: <CABdc3Wq=DsQbcF3Wptg8k0qwu5S4ht7wynBobRFkuqAKME1iaQ@mail.gmail.com>
To: Marco Pivetta <ocramius@gmail.com>
Cc: Wes <netmo.php@gmail.com>, PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a1141ddd2df82c8054632d621
Subject: Re: [PHP-DEV] Unsetting declared fields
From: michal@brzuchalski.com (=?UTF-8?Q?Micha=C5=82_Brzuchalski?=)

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As I am familiar with those interceptions, I tend to point out some dirty
hacks
when reflection tells you property exists while getting notice on set, see
https://3v4l.org/VDMHm

<?php

class Foo
{
    public $bar =3D 'bar';
    public $baz =3D 'baz';
}

class FooHack extends Foo
{
    public function __construct(Foo $wrapped)
    {
        unset($this->bar);
    }
}

$foo =3D new FooHack(new Foo);

$reflectionFooBar =3D new \ReflectionProperty(Foo::class, 'bar');
var_dump((new ReflectionClass(Foo::class))->getProperties());
var_dump($reflectionFooBar->getValue($foo));
var_dump(
    property_exists(FooHack::class, 'bar'),
    property_exists($foo, 'bar')
);

Funny PHP7 has different behaviour from 7.0.7 - 7.1 with raising a notice.
I may be just looking for dirty example without purpose right now so, don't
listen to me.
But I do feel like this could bring someone crazy when something should
exists while it's not.
Those property_exists($foo, 'bar') shouldn't return false in that example?!

2017-01-16 10:17 GMT+01:00 Marco Pivetta <ocramius@gmail.com>:

> On Mon, Jan 16, 2017 at 9:49 AM, Micha=C5=82 Brzuchalski <
> michal@brzuchalski.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 stil=
l
>> 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 caus=
e
>> 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 $foo =3D 1=
0;)
>>> to
>>> > be removed entirely through unset (eg unset($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
>>> allowed
>>> > for fields that are explicitly declared. I think unset() should set t=
he
>>> > 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 peopl=
e
>>> not
>>> > doing nasty stuff with our code. This might sound ironic it is
>>> actually 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/
> cce5477857504997baf3168974b8f1283516a686/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/
>



--=20
regards / pozdrawiam,
--
Micha=C5=82 Brzuchalski
about.me/brzuchal
brzuchalski.com

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