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Date: Fri, 13 Aug 2021 16:56:54 +0200
Message-ID: <CAF+90c81nB7SzRYBQtQZAuDKbHFToa7Jc3LVGNgrxB4uGtTh9g@mail.gmail.com>
To: Marc <marc@mabe.berlin>
Cc: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="000000000000ecb91005c9721073"
Subject: Re: [PHP-DEV] readonly properties
From: nikita.ppv@gmail.com (Nikita Popov)

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On Thu, Aug 12, 2021 at 9:16 PM Marc <marc@mabe.berlin> wrote:

> Hi,
>
> As 8.1 adds readonly properties I wonder which build-in properties
> should be defined readonly.
>
> Currently I could find build-in readonly properties only on PDO and DOM.
>
>
> Very incomplete list where readonly properties could make sense:
>
> 1. Enum properties:
>
> enum Test:string {
>      case TEST = 'test';
> }
>
> $case = TEST::TEST;
> $refl = (new ReflectionObject($case))->getProperty('value');
> var_dump($refl->isReadOnly());  // false
> var_dump($refl->isPublic());  // true
> $case->value = 'foo'; // Fatal error: Uncaught Error: Enum properties
> are immutable
>

Yeah, these are a perfect use case for "readonly". Done in
https://github.com/php/php-src/commit/caefc6a50789295b0993c4e657c825484650172a.
This actually fixes a bug, because the homegrown "readonly" implementation
for enums was not quite correct.


> 2. DateInterval->days
>
> $interval = (new DateTime())->diff(new DateTime());
> var_dump($interval->days); // 0
> $refl = (new ReflectionObject($interval))->getProperty('days');
> var_dump($refl->isReadOnly()); // false
> var_dump($refl->isPublic()); // true
> $interval->days = 2;
> var_dump($interval->days);  // 0
>

The DateInterval properties are currently implemented as getters/setters on
some internal state. Some of those are getter-only, but probably not fully
immutable.

3. Exception properties
>
> Exception properties are protected but does it really make sense to be
> able to modify an exception property after initialization?
>
> I know this would be a BC break :(
>

There is definitely code out there relying on modifying both protected and
private Exception properties, I don't think we want to touch these without
cause.

Regards,
Nikita

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