get_class_vars() and typed properties

6 years ago by Benjamin Morel — view source

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Hi Internals, I just noticed the following behaviour:

class A {
    public int $a;
    public ?int $b;
    public ?int $c = null;
}

$a = new A;

var_export(get_object_vars($a));
var_export(get_class_vars('A'));

Result:

array (
    'c' => NULL,
  )
array (
  'a' => NULL,
  'b' => NULL,
  'c' => NULL,
)

Is this discrepancy expected? IMO get_object_vars() does the right thing
and does not include uninitialized properties in the result array.

OTOH, get_class_vars() returns null when the property is uninitialized,
which I think is confusing (especially when null is not a valid value for
the property), and I feel like this does not respect the documented
contract: "get_class_vars — Get the default properties of the class" when
null is not the default value.

I did not file a bug yet as I wanted to gather some feedback first.
Thank you.

— Benjamin

6 years ago by Nicolas Grekas — view source

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Le dim. 18 août 2019 à 11:59, Benjamin Morel benjamin.morel@gmail.com a
écrit :

Hi Internals, I just noticed the following behaviour:
class A {
    public int $a;
    public ?int $b;
    public ?int $c = null;
}

$a = new A;

var_export(get_object_vars($a));
var_export(get_class_vars('A'));
Result:
array (
    'c' => NULL,
  )
array (
  'a' => NULL,
  'b' => NULL,
  'c' => NULL,
)
Is this discrepancy expected? IMO get_object_vars() does the right thing
and does not include uninitialized properties in the result array.

OTOH, get_class_vars() returns null when the property is uninitialized,
which I think is confusing (especially when null is not a valid value for
the property), and I feel like this does not respect the documented
contract: "get_class_vars — Get the default properties of the class" when
null is not the default value.

I did not file a bug yet as I wanted to gather some feedback first.
Thank you.

— Benjamin

See https://bugs.php.net/78319
get_class_var() does the most useful thing, thus the correct one to me and
the use cases I have.

Nicolas

6 years ago by Rowan Collins — view source

unread

Le dim. 18 août 2019 à 11:59, Benjamin Morel benjamin.morel@gmail.com
a
écrit :
Hi Internals, I just noticed the following behaviour:
class A {
    public int $a;
    public ?int $b;
    public ?int $c = null;
}

$a = new A;

var_export(get_object_vars($a));
var_export(get_class_vars('A'));
Result:
array (
    'c' => NULL,
  )
array (
  'a' => NULL,
  'b' => NULL,
  'c' => NULL,
)

See https://bugs.php.net/78319
get_class_var() does the most useful thing, thus the correct one to me
and
the use cases I have.

This is a nice example of something I said when typed properties were being added: "uninitialised" is a new special state, distinct from "non-existent" and "null". As such, a non-nullable typed property without default value is impossible to represent accurately without having a representation of that state.

One rather ugly possiblity in this case would be to have the values returned be "uninitialized", so that accessing the array keys was valid, but accessing the values gave an Unitialized Value Error. That would be pretty horrible for backwards compatibility, though, particularly for get_class_properties, where there's no chance for the constructor to run and set up a real value.

Regards,

--
Rowan Collins
[IMSoP]