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Date: Fri, 13 Aug 2021 17:53:36 +0200
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Subject: Re: [PHP-DEV] readonly properties
From: marc@mabe.berlin (Marc)


On 8/13/21 4:56 PM, Nikita Popov wrote:
> 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.

WOW this was fast. Less code and even a bugfix +1

>
>> 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.

I was referring to the property "days" only as this is a non writable 
value generated on "DateTime->diff".

As you can see in the snipped it doesn't allow to modify days but it 
also doesn't fail which seems wrong to me.

I don't have much knowledge about internals but would it be possible to 
define "public readonly int|false $days" not using getters/setters and 
keep all other properties as it?


>
> 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.

Yea you are probably right - it would be a heavy BC break for not much 
profit.

> Regards,
> Nikita
>

Thank you very much Nikita!