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Subject: Re: [PHP-DEV] [RFC] Readonly property hooks
Date: Sat, 19 Jul 2025 12:09:09 +0200
In-Reply-To: <247034b6-04cf-4f3e-a145-a30171af8c12@app.fastmail.com>
Cc: erictnorris@gmail.com,
 Nicolas Grekas <nicolas.grekas+php@gmail.com>,
 Larry Garfield <larry@garfieldtech.com>,
 =?utf-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>,
 php internals <internals@lists.php.net>
To: Rob Landers <rob@bottled.codes>
References: <378cd8b0-c4a8-4e53-b0bd-e9e4f30a454d@app.fastmail.com>
 <77128196-8D53-40D6-9BB7-77160AD71ED9@gmail.com>
 <247034b6-04cf-4f3e-a145-a30171af8c12@app.fastmail.com>
From: claude.pache@gmail.com (Claude Pache)


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> Le 19 juil. 2025 =C3=A0 09:46, Rob Landers <rob@bottled.codes> a =
=C3=A9crit :
>=20
>=20
>=20
> On Sat, Jul 19, 2025, at 03:04, Claude Pache wrote:
>>=20
>>=20
>>=20
>>> Le 19 juil. 2025 =C3=A0 00:41, Rob Landers <rob@bottled.codes> a =
=C3=A9crit :
>>>=20
>>> The original author (Nikita) suggested that there's nothing in the =
original design that precludes accessors -- and highlights languages =
where there are both and they are doing just fine more than 5 years =
later.
>>>=20
>>=20
>> Hi Rob,
>>=20
>> It is indeed entirely reasonable to have both readonly properties and =
hooked properties (aka accessors), and today PHP has indeed both of them =
(and even asymmetric visibility on top of that, as a separate feature =
contrarily to C#). But it doesn=E2=80=99t mean that it is reasonable for =
the *same* property to be *both* readonly and hooked, which is the point =
that is currently disputed. =E2=80=94 What do the other languages allow? =
Is it possible to define a readonly property with a user-defined getter? =
(Disclaimer: Even if one of them allows such a thing, I=E2=80=99ll still =
think that it is a bad idea.)
>>=20
>> =E2=80=94Claude=20
>=20
> Hey Claude,
>=20
> =46rom what I've seen in other languages, this combination is fairly =
common and not inherently poblematic.
>=20
> - C# allows get hooks with user-defined logic, even in readonly =
structs.
> - Kotlin uses val with a get() body, which is readonly from the =
consumer's perspective, even though the value is computed.
> - TypeScript allows a get-only accessor which acts readonly.
> - Swift also allows get-only computed accessors/hooks.

Hi Rob,=20

The main problem is that we don=E2=80=99t agree on the meaning of =
=E2=80=9Creadonly property=E2=80=9D.

I=E2=80=99ve check TypeScript:

* It has getters and setters, which correspond to PHP get/set hooks =
without backing store.

* Separately, it also has a `readonly` modifier that can be applied to =
properties; the semantics is that such a property may be initialised =
either at declaration or inside the constructor, but cannot be modified =
afterwards. That corresponds approximatively to PHP readonly properties.

* But a =E2=80=9Cget-only accessor=E2=80=9D is not the same thing as a =
=E2=80=9Creadonly property=E2=80=9D in the specific sense of =E2=80=9Da =
property decorated with the `readonly` modifier=E2=80=9D. Also, you =
cannot add the readonly modifier to a get accessor.

=E2=80=94Claude


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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; =
charset=3Dutf-8"></head><body style=3D"overflow-wrap: break-word; =
-webkit-nbsp-mode: space; line-break: after-white-space;"><br =
id=3D"lineBreakAtBeginningOfMessage"><div><br><blockquote =
type=3D"cite"><div>Le 19 juil. 2025 =C3=A0 09:46, Rob Landers =
&lt;rob@bottled.codes&gt; a =C3=A9crit :</div><br =
class=3D"Apple-interchange-newline"><div><title></title><div><div><br></di=
v><div><br></div><div>On Sat, Jul 19, 2025, at 03:04, Claude Pache =
wrote:</div><blockquote type=3D"cite" id=3D"qt" style=3D""><div =
dir=3D"ltr"><div dir=3D"ltr"><br></div><div dir=3D"ltr"><br></div><div =
dir=3D"ltr"><div><br></div><blockquote type=3D"cite"><div>Le 19 juil. =
2025 =C3=A0 00:41, Rob Landers &lt;rob@bottled.codes&gt; a =
=C3=A9crit&nbsp;:</div></blockquote></div><blockquote type=3D"cite"><div =
dir=3D"ltr"><div class=3D"qt-align-start" =
style=3D"text-align:start;"><br></div><div class=3D"qt-align-start" =
style=3D"text-align:start;">The original author (Nikita) suggested that =
there's nothing in the original design that precludes accessors -- and =
highlights languages where there are both and they are doing just fine =
more than 5 years later.</div><div class=3D"qt-align-start" =
style=3D"text-align:start;"><br></div></div></blockquote><div><br></div><d=
iv>Hi Rob,</div><div><br></div><div>It is indeed entirely reasonable to =
have both readonly properties and hooked properties (aka accessors), and =
today PHP has indeed both of them (and even asymmetric visibility on top =
of that, as a separate feature contrarily to C#). But it doesn=E2=80=99t =
mean that it is reasonable for the *same* property to be *both* readonly =
and hooked, which is the point that is currently disputed. =E2=80=94 =
What do the other languages allow? Is it possible to define a readonly =
property with a user-defined getter? (Disclaimer: Even if one of them =
allows such a thing, I=E2=80=99ll still think that it is a bad =
idea.)</div><div><br></div><div>=E2=80=94Claude&nbsp;</div></div></blockqu=
ote><div><br></div><div>Hey Claude,</div><div><br></div><div>=46rom what =
I've seen in other languages, this combination is fairly common and =
not&nbsp;inherently poblematic.</div><div><br></div><div>- C# allows get =
hooks with user-defined logic, even in readonly structs.</div><div>- =
Kotlin uses val with a get() body, which is readonly from the consumer's =
perspective, even though the value is computed.</div><div>- TypeScript =
allows a get-only accessor which acts readonly.</div><div>- Swift also =
allows get-only computed =
accessors/hooks.</div></div></div></blockquote><div><br></div><div>Hi =
Rob,&nbsp;</div><div><br></div><div>The main problem is that we don=E2=80=99=
t agree on the meaning of =E2=80=9Creadonly =
property=E2=80=9D.</div><div><br></div><div>I=E2=80=99ve check =
TypeScript:</div><div><br></div><div>* It has getters and setters, which =
correspond to PHP get/set hooks without backing =
store.</div><div><br></div><div>* Separately, it also has a `readonly` =
modifier that can be applied to properties; the semantics is that such a =
property may be initialised either at declaration or inside the =
constructor, but cannot be modified afterwards. That corresponds =
approximatively to PHP readonly properties.</div><div><br></div><div>* =
But a =E2=80=9Cget-only accessor=E2=80=9D is not the same thing as a =
=E2=80=9Creadonly property=E2=80=9D in the specific sense of =E2=80=9Da =
property decorated with the `readonly` modifier=E2=80=9D. Also, you =
cannot add the readonly modifier to a get =
accessor.</div><div><br></div><div>=E2=80=94Claude</div><div><br></div></d=
iv></body></html>=

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