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Date: Thu, 31 Jul 2025 10:46:50 +0200
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Subject: [PHP-DEV] references & arrays + hooks
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From: rob@bottled.codes ("Rob Landers")

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Hello internals:

Currently, this is not allowed by PHP:

class Foo {
  public function __construct(
      public string &$ref { get =3D> $this->ref ?? 'null'; set =3D> $thi=
s->ref =3D $value; }
  ) {}
}

$var =3D 'hello';
$foo =3D new Foo($var);
$var =3D "world";

echo $foo->ref;
https://3v4l.org/JRArK

Currently, you have to emulate it like so:

class Foo {

  public string $ref {
      get =3D> $this->_ref;
      set =3D> $this->_ref =3D $value;
  }

  public function __construct(
      private string &$_ref,
  ) {}
}

$var =3D 'hello';
$foo =3D new Foo($var);
$foo->ref =3D 'world';

echo $var;
https://3v4l.org/0cC0S

After the release, I'd like to propose an RFC that allows using referenc=
es with hooks:

A hooked reference variable is a callable/closure under the hood (techni=
cally, a reference to the actual hook methods) that can be used like a v=
alue. Reading from it calls the ::get() method, and setting to it calls =
the ::set($value) method. If the callable were to be written in PHP, it =
might look something like the following psuedo code:

function hookRef(...$args) use (&$backedValue) {
  if(empty($args)) return $backedValue::get();
  $backedValue =3D $backedValue::set(array_first($args));
}

In simplified terms, the engine, upon detecting a read/write to a hooked=
 reference (eg, a standalone variable pointing to a hooked property), in=
stead of doing typical variable access, it will call the bound closure w=
ith the appropriate arguments. This will effectively allow hooks to be r=
eferences.

This would also handle the case for arrays, which appears to require the=
 same plumbing to exist.

Downsides:
 1. this will probably necessitate a new zval type, determined at runtim=
e (it will not be exposed to users).
 2. there are a lot of ways to access/write to a variable (especially on=
ce you consider arrays) thus it will touch a lot of the engine.
Thoughts? Concerns? Suggestions?

=E2=80=94 Rob
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<!DOCTYPE html><html><head><title></title></head><body><div>Hello intern=
als:</div><div><br></div><div>Currently, this is not allowed by PHP:</di=
v><div><br></div><div>class Foo {</div><div>&nbsp; public function __con=
struct(</div><div>&nbsp; &nbsp; &nbsp; public string &amp;$ref { get =3D=
&gt; $this-&gt;ref ?? 'null'; set =3D&gt; $this-&gt;ref =3D $value; }</d=
iv><div>&nbsp; ) {}</div><div>}</div><div><br></div><div>$var =3D 'hello=
';</div><div>$foo =3D new Foo($var);</div><div>$var =3D "world";</div><d=
iv><br></div><div>echo $foo-&gt;ref;</div><div><a href=3D"https://3v4l.o=
rg/JRArK">https://3v4l.org/JRArK</a></div><div><br></div><div>Currently,=
 you have to emulate it like so:</div><div><br></div><div>class Foo {</d=
iv><div><br></div><div>&nbsp; public string $ref {</div><div>&nbsp;&nbsp=
;&nbsp;&nbsp;&nbsp; get =3D&gt; $this-&gt;_ref;</div><div>&nbsp;&nbsp;&n=
bsp;&nbsp;&nbsp; set =3D&gt; $this-&gt;_ref =3D $value;</div><div>&nbsp;=
 }</div><div><br></div><div>&nbsp; public function __construct(</div><di=
v>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; private string &amp;$_ref,</div><div>&n=
bsp; ) {}</div><div>}</div><div><br></div><div>$var =3D 'hello';</div><d=
iv>$foo =3D new Foo($var);</div><div>$foo-&gt;ref =3D 'world';</div><div=
><br></div><div>echo $var;<br></div><div>https://3v4l.org/0cC0S<br></div=
><div><br></div><div>After the release, I'd like to propose an RFC that =
allows using references with hooks:</div><div><br></div><div>A hooked re=
ference variable is a callable/closure under the hood (technically, a re=
ference to the actual hook methods) that can be used like a value. Readi=
ng from it calls the ::get() method, and setting to it calls the ::set($=
value) method. If the callable were to be written in PHP, it might look =
something like the following psuedo code:</div><div><br></div><div>funct=
ion hookRef(...$args) use (&amp;$backedValue) {</div><div>&nbsp; if(empt=
y($args)) return $backedValue::get();</div><div>&nbsp; $backedValue =3D =
$backedValue::set(array_first($args));</div><div>}</div><div><br></div><=
div>In simplified terms, the engine, upon detecting a read/write to a ho=
oked reference (eg, a standalone variable pointing to a hooked property)=
, instead of doing typical variable access, it will call the bound closu=
re with the appropriate arguments. This will effectively allow hooks to =
be references.</div><div><br></div><div>This would also handle the case =
for arrays, which appears to require the same plumbing to exist.</div><d=
iv><br></div><div>Downsides:<br></div><ol><li>this will probably necessi=
tate a new zval type, determined at runtime (it will not be exposed to u=
sers).</li><li>there are a lot of ways to access/write to a variable (es=
pecially once you consider arrays) thus it will touch a lot of the engin=
e.</li></ol><div>Thoughts? Concerns? Suggestions?</div><div><br></div><d=
iv id=3D"sig121229152">=E2=80=94 Rob</div></body></html>
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