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Date: Wed, 03 Sep 2025 22:44:58 +0200
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Subject: [PHP-DEV] enum flag backed enum
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From: rob@bottled.codes ("Rob Landers")

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Hello internals,

I would like to propose a new type of backed enum: flag. This is an inte=
ger-backed enum that requires power-of-two values that can be combined w=
ith the bitwise operators to be used as flags.

In some core functions, it might look like this:

enum JSON_FLAG: flag {
  case None =3D 0;
  case ThrowOnError =3D 0x1 << 1;
  // etc.
  case PrettyPrint =3D 0x01 << 4;
  // etc.
}

function json_decode(string $data, bool $assoc =3D false, int $depth =3D=
 512, JSON_FLAG|int $options =3D JSON_FLAG::None) {}

json_decode($data, options: JSON_FLAG::ThrowOnError | JSON_FLAG::PrettyP=
rint);

Note that the goal here isn=E2=80=99t so much to save typing space, as i=
t is to provide easier discoverability through IDEs, better type safety,=
 and better ergonomics in the language overall.

Attempting to use a backed value that is not a power-of-two would result=
 in a compilation error. Bitwise operations are performed as though they=
=E2=80=99re performed on a regular integer.

What do you think?

I couldn=E2=80=99t find any similar proposals (listed on the RFC page) b=
efore proposing this on the list, so if you=E2=80=99re working on this, =
please speak up; I=E2=80=99d like to join forces.

=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>I would like to propose a new type of back=
ed enum: flag. This is an integer-backed enum that requires power-of-two=
 values that can be combined with the bitwise operators to be used as fl=
ags.</div><div><br></div><div>In some core functions, it might look like=
 this:</div><div><br></div><div>enum JSON_FLAG: flag {</div><div>&nbsp; =
case None =3D 0;</div><div>&nbsp; case ThrowOnError =3D 0x1 &lt;&lt; 1;<=
/div><div>&nbsp; // etc.</div><div>&nbsp; case PrettyPrint =3D 0x01 &lt;=
&lt; 4;</div><div>&nbsp; // etc.</div><div>}</div><div><br></div><div>fu=
nction json_decode(string $data, bool $assoc =3D false, int $depth =3D 5=
12, JSON_FLAG|int $options =3D JSON_FLAG::None) {}</div><div><br></div><=
div>json_decode($data, options: JSON_FLAG::ThrowOnError | JSON_FLAG::Pre=
ttyPrint);</div><div><br></div><div>Note that the goal here isn=E2=80=99=
t so much to save typing space, as it is to provide easier discoverabili=
ty through IDEs, better type safety, and better ergonomics in the langua=
ge overall.</div><div><br></div><div>Attempting to use a backed value th=
at is not a power-of-two would result in a compilation error. Bitwise op=
erations are performed as though they=E2=80=99re performed on a regular =
integer.</div><div><br></div><div>What do you think?</div><div><br></div=
><div>I couldn=E2=80=99t find any similar proposals (listed on the RFC p=
age) before proposing this on the list, so if you=E2=80=99re working on =
this, please speak up; I=E2=80=99d like to join forces.<br></div><div><b=
r></div><div id=3D"sig121229152">=E2=80=94 Rob</div></body></html>
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