Unsetting declared fields

8 years ago by netmo.php@gmail.com — view source

unread

Hello elephpants.

Currently PHP allows explicitly declared fields (eg public $foo = 10;) to
be removed entirely through unset (eg unset($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 allowed
for fields that are explicitly declared. I think unset() should set the
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 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?

8 years ago by Marco Pivetta — view source

unread

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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = new FooInterceptor(new Foo);

var_dump($foo->bar);

You can see a working example at https://3v4l.org/UtugD

This behavior is protected from regressions since PHP 5.4, but has been
working since 5.0:
https://github.com/php/php-src/blob/cd2b462a2742c79256668d4736644e34573c33d9/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/

Hello elephpants.

Currently PHP allows explicitly declared fields (eg public $foo = 10;) to
be removed entirely through unset (eg unset($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 allowed
for fields that are explicitly declared. I think unset() should set the
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 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?

8 years ago by Marco Pivetta — view source

unread

Almost forgot: these examples apply also to private and protected
properties. That's currently the only way to make the behavior consistent
across friend objects (same scope).

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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = new FooInterceptor(new Foo);

var_dump($foo->bar);

You can see a working example at https://3v4l.org/UtugD

This behavior is protected from regressions since PHP 5.4, but has been
working since 5.0: https://github.com/php/php-src/blob/
cd2b462a2742c79256668d4736644e34573c33d9/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/

Hello elephpants.

Currently PHP allows explicitly declared fields (eg public $foo = 10;) to
be removed entirely through unset (eg unset($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 allowed
for fields that are explicitly declared. I think unset() should set the
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 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?

Marco Pivetta

http://twitter.com/Ocramius

http://ocramius.github.com/

8 years ago by netmo.php@gmail.com — view source

unread

I do that too... but I feel bad for doing it :P Property accessors would be
great to have...

8 years ago by michal@brzuchalski.com — view source

unread

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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = 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 = new ReflectionClass(FooInterceptor::class);
$property = $class->getProperty('bar');
var_dump($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/cd2b462a2742c79256668d4736644e
34573c33d9/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/

Hello elephpants.

Currently PHP allows explicitly declared fields (eg public $foo = 10;) to
be removed entirely through unset (eg unset($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 allowed
for fields that are explicitly declared. I think unset() should set the
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 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?

--
regards / pozdrawiam,

Michał Brzuchalski
about.me/brzuchal
brzuchalski.com

8 years ago by michal@brzuchalski.com — view source

unread

2017-01-16 9:49 GMT+01:00 Michał Brzuchalski michal@brzuchalski.com:

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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = 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 = new ReflectionClass(FooInterceptor::class);
$property = $class->getProperty('bar');
var_dump($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/

Hello elephpants.

Currently PHP allows explicitly declared fields (eg public $foo = 10;)
to
be removed entirely through unset (eg unset($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 allowed
for fields that are explicitly declared. I think unset() should set the
field to null if it's declared in the class, and remove the field
altogether only if it was defined dynamically.

Actually this sounds quite reasonably. Such properties may be set to null
and if someone doesn't want them
at debug can use __debugInfo magic method to cut it off.
I'm +1 for setting null class properties and unsetting dynamic proprties.
@Wes you've got my very, humble support :)

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 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?

--
regards / pozdrawiam,

Michał Brzuchalski
about.me/brzuchal
brzuchalski.com

--
regards / pozdrawiam,

Michał Brzuchalski
about.me/brzuchal
brzuchalski.com

8 years ago by Marco Pivetta — view source

unread

On Mon, Jan 16, 2017 at 9:49 AM, Michał 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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = 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 = new ReflectionClass(FooInterceptor::class);
$property = $class->getProperty('bar');
var_dump($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/

Hello elephpants.

Currently PHP allows explicitly declared fields (eg public $foo = 10;)
to
be removed entirely through unset (eg unset($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 allowed
for fields that are explicitly declared. I think unset() should set the
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 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 Michał,

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 = 'baz';
}

$foo = new FooInterceptor(new Foo);

$reflectionFooBar = 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/

8 years ago by michal@brzuchalski.com — view source

unread

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 = 'bar';
public $baz = 'baz';
}

class FooHack extends Foo
{
public function __construct(Foo $wrapped)
{
unset($this->bar);
}
}

$foo = new FooHack(new Foo);

$reflectionFooBar = new \ReflectionProperty(Foo::class, 'bar');
var_dump((new ReflectionClass(Foo::class))->getProperties());
var_dump($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, Michał 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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = 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 = new ReflectionClass(FooInterceptor::class);
$property = $class->getProperty('bar');
var_dump($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/

Hello elephpants.

Currently PHP allows explicitly declared fields (eg public $foo = 10;)
to
be removed entirely through unset (eg unset($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
allowed
for fields that are explicitly declared. I think unset() should set the
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
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 Michał,

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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = new FooInterceptor(new Foo);

$reflectionFooBar = 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/

--
regards / pozdrawiam,

Michał Brzuchalski
about.me/brzuchal
brzuchalski.com

8 years ago by Marco Pivetta — view source

unread

Hi Michał,

On Mon, Jan 16, 2017 at 10:30 AM, Michał Brzuchalski <michal@brzuchalski.com

wrote:

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 = 'bar';
public $baz = 'baz';
}

class FooHack extends Foo
{
public function __construct(Foo $wrapped)
{
unset($this->bar);
}
}

$foo = new FooHack(new Foo);

$reflectionFooBar = new \ReflectionProperty(Foo::class, 'bar');
var_dump((new ReflectionClass(Foo::class))->getProperties());
var_dump($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.

Yes, some cleanups were applied to PHP 7.1 (Nikic worked on them, I think).
Specifically around trying to access reflection properties across
incompatible object types. Unsure if that also touched property_exists()

I may be just looking for dirty example without purpose right now so, don't
listen to me.

No, that's fine. These are dirty hacks, but it really is the only
(currently) available way to build userland property accessors. Without
this kind of approach, the only alternative is relying on
https://pecl.php.net/package/AOP, and that's not really something that is
going to happen.

But I do feel like this could bring someone crazy when something should
exists while it's not.

This is not something that users would do directly. AOP-ish libraries are
extremely well tested in these scenarios, because if something magic breaks
it is really hard to understand what is going on.

Those property_exists($foo, 'bar') shouldn't return false in that example?!

I'd say that property_exists() should always return true for static
(class definition) defined fields, since the primary use-case for
property_exists() is to provide information for consumers of a certain
object for BC/FC. Most frameworks/libraries rely on function_exists(),
method_exists() and property_exists() to skip tests, run tests, load
polyfills, etc.

My best guess is that the API shouldn't change though. That's the safest BC
approach, whereas new behavior can be defined with a completely new
function (for example: property_is_statically_defined(),
property_value_is_assigned(), etc.).

2017-01-16 10:17 GMT+01:00 Marco Pivetta ocramius@gmail.com:

On Mon, Jan 16, 2017 at 9:49 AM, Michał 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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = 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 = new ReflectionClass(FooInterceptor::class);
$property = $class->getProperty('bar');
var_dump($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/

Hello elephpants.

Currently PHP allows explicitly declared fields (eg public $foo =
10;)
to
be removed entirely through unset (eg unset($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
allowed
for fields that are explicitly declared. I think unset() should set
the
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
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 Michał,

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 = 'baz';
}

class FooInterceptor extends Foo
{
private $wrapped;
public function __construct(Foo $wrapped)
{
$this->wrapped = $wrapped;
unset($this->bar);
}
public function __get(string $name)
{
var_dump('reading ' . $name);
return $this->wrapped->$name;
}
}

$foo = new FooInterceptor(new Foo);

$reflectionFooBar = 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/

Marco Pivetta

http://twitter.com/Ocramius

http://ocramius.github.com/

Unsetting declared fields

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