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Subject: Re: [PHP-DEV] [RFC] Readonly property hooks
Date: Fri, 11 Jul 2025 09:25:33 +0200
In-Reply-To: <9D5043B2-1589-4FD5-B289-6E98FB1177BE@nicksdot.dev>
Cc: Larry Garfield <larry@garfieldtech.com>,
 php internals <internals@lists.php.net>
To: Nick <php@nicksdot.dev>
References: <1e8634d7-ac1a-4025-b4e2-1948aabf5251@app.fastmail.com>
 <9D5043B2-1589-4FD5-B289-6E98FB1177BE@nicksdot.dev>
From: claude.pache@gmail.com (Claude Pache)


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> Le 11 juil. 2025 =C3=A0 06:30, Nick <php@nicksdot.dev> a =C3=A9crit :
>=20
> Hey all,
>=20
>> On 8. Jun 2025, at 11:16, Larry Garfield <larry@garfieldtech.com> =
wrote:
>>=20
>> As Nick has graciously provided an implementation, we would like to =
open discussion on this very small RFC to allow `readonly` on backed =
properties even if they have a hook defined.
>>=20
>> https://wiki.php.net/rfc/readonly_hooks
>>=20
>> --=20
>>  Larry Garfield
>>  larry@garfieldtech.com
>=20
> To not get this buried in individual answers to others:
>=20
> I came up with two alternative implementations which cache the =
computed `get` hook value.
> One leverages separate cache properties, the other writes directly to =
the backing store.
>=20
> Links to the alternative branches can be found in the description of =
the original PR.
> https://github.com/php/php-src/pull/18757
>=20
> I believe that these are fair solutions to address the concerns that =
came up in the discussion, and I hope people will agree.
>=20
> Cheers,
> Nick


Hi Nick,

I think that the second alternative described as:

=E2=80=9CCache computed get hook to it's backing store; never run the =
hook again=E2=80=9D

is near the most reasonable from my point of view (basing my judgment on =
the description, as I have not looked the actual implementation), =
although there are still some concerns.

Advantages of that approach:

1. relatively to the first alternative solution: there is indeed no =
point to have a cache separate from the backing-store, as the =
backing-store is supposed to play that role in most cases;

2. relatively to the manual =E2=80=9C??=3D=E2=80=9D pattern, it works =
correctly with nullable properties.

Here are my remaining concerns:

A. It may be confusing to have a getter that is not always called.

B. The idea of returning the value directly from the backing-store if =
initialised is useful also for non-readonly properties. (That can be =
emulated with the =E2=80=9C??=3D=E2=80=9D pattern, but only if the =
property is not nullable.)

Both concerns may be resolved with the following amendment:

* Introduce a `cached` modifier, that enables the caching semantics =
(i.e., not executing the getter if the backing-store is initialised).

The example from the RFC would be written as:

```php
readonly class LazyProduct extends Product {

   private DbConnection $dbApi;
=20
   private string $categoryId;
=20
   public Category $category {
       cached get =3D> $this->dbApi->loadCategory($this->categoryId);
   }
}
```

The `cached` modifier may be applied to any get hook, but it is =
mandatory if the property is readonly.

(In practice, the =E2=80=9Ccached get hook=E2=80=9D corresponds to my =
originally proposed =E2=80=9Cinit hook=E2=80=9D, but with the advantage =
of not having a separate hook.)=20

=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 11 juil. 2025 =C3=A0 06:30, Nick =
&lt;php@nicksdot.dev&gt; a =C3=A9crit :</div><br =
class=3D"Apple-interchange-newline"><div><meta http-equiv=3D"content-type"=
 content=3D"text/html; charset=3Dus-ascii"><div style=3D"overflow-wrap: =
break-word; -webkit-nbsp-mode: space; line-break: =
after-white-space;">Hey all,<br =
id=3D"lineBreakAtBeginningOfMessage"><div><br><blockquote =
type=3D"cite"><div>On 8. Jun 2025, at 11:16, Larry Garfield =
&lt;larry@garfieldtech.com&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div><div>As Nick has graciously =
provided an implementation, we would like to open discussion on this =
very small RFC to allow `readonly` on backed properties even if they =
have a hook =
defined.<br><br>https://wiki.php.net/rfc/readonly_hooks<br><br>-- <br> =
&nbsp;Larry Garfield<br> =
&nbsp;larry@garfieldtech.com<br></div></div></blockquote></div><br><div>To=
 not get this buried in individual answers to =
others:</div><div><br></div><div>I came up with two alternative =
implementations which cache the computed `get` hook value.</div><div>One =
leverages separate cache properties, the other writes directly to the =
backing store.</div><div><br></div><div>Links to the alternative =
branches can be found in the description of the original =
PR.</div><div>https://github.com/php/php-src/pull/18757</div><div><br></di=
v><div>I believe that these are fair solutions to address the concerns =
that came up in the discussion, and I hope people will =
agree.</div><div><br></div><div><b>Cheers,</b></div><div>Nick</div></div><=
/div></blockquote></div><br><div><br></div><div>Hi =
Nick,</div><div><br></div><div>I think that the second alternative =
described as:</div><div><br></div><div>=E2=80=9CCache computed get hook =
to it's backing store; never run the hook =
again=E2=80=9D</div><div><br></div><div>is near the most reasonable from =
my point of view (basing my judgment on the description, as I have not =
looked the actual implementation), although there are still some =
concerns.</div><div><br></div><div>Advantages of that =
approach:</div><div><br></div><div>1. relatively to the first =
alternative solution: there is indeed no point to have a cache separate =
from the backing-store, as the backing-store is supposed to play that =
role in most cases;</div><div><br></div><div>2. relatively to the manual =
=E2=80=9C??=3D=E2=80=9D pattern, it works correctly with nullable =
properties.</div><div><br></div><div>Here are my remaining =
concerns:</div><div><br></div><div>A. It may be confusing to have a =
getter that is not always called.</div><div><br></div><div>B. The idea =
of returning the value directly from the backing-store if initialised is =
useful also for non-readonly properties. (That can be emulated with the =
=E2=80=9C??=3D=E2=80=9D pattern, but only if the property is not =
nullable.)</div><div><br></div><div>Both concerns may be resolved with =
the following amendment:</div><div><br></div><div>* Introduce a `cached` =
modifier, that enables the caching semantics (i.e., not executing the =
getter if the backing-store is =
initialised).</div><div><br></div><div>The example from the RFC would be =
written as:</div><div><br></div><div>```php</div><div>readonly class =
LazyProduct extends Product {</div><div><br></div><div>&nbsp; =
&nbsp;private DbConnection $dbApi;</div><div>&nbsp;</div><div>&nbsp; =
&nbsp;private string $categoryId;</div><div>&nbsp;</div><div>&nbsp; =
&nbsp;public Category $category {</div><div>&nbsp; &nbsp; &nbsp; =
&nbsp;cached get =3D&gt; =
$this-&gt;dbApi-&gt;loadCategory($this-&gt;categoryId);</div><div>&nbsp; =
&nbsp;}</div><div>}</div><div>```</div><div><br></div><div>The `cached` =
modifier may be applied to any get hook, but it is mandatory if the =
property is readonly.</div><div><br></div><div>(In practice, the =
=E2=80=9Ccached get hook=E2=80=9D corresponds to my originally proposed =
=E2=80=9Cinit hook=E2=80=9D, but with the advantage of not having a =
separate =
hook.)&nbsp;</div><div><br></div><div>=E2=80=94Claude</div><div><br></div>=
<div><br></div><div><br></div><div><br></div></body></html>=

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