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Date: Mon, 6 Jan 2020 14:17:10 -0500
Cc: PHP internals <internals@lists.php.net>
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To: tyson andre <tysonandre775@hotmail.com>
Subject: Re: [PHP-DEV] Initializing constants once, with code?
From: mike@newclarity.net (Mike Schinkel)

> On Jan 5, 2020, at 5:04 PM, tyson andre <tysonandre775@hotmail.com> =
wrote:
>=20
> I have a work in progress wrapper for allowing const-like syntax for =
global constants `static const X =3D $dynamicExpression;`.
> This can be seen in https://github.com/TysonAndre/php-src/pull/10

Thanks for replying and including this.  Nice work.


> - Eagerly initialized dynamic constants are easier to reason about in =
some ways (e.g. fetching the constant of an already fetched class is =
less likely to cause pauses or exceptions.)
>  This makes un-noticed errors in rare code paths less likely.
> - Attempting to support function calls, property accesses, class =
constant accesses (e.g. inherited), and variables in class constants =
recursively and/or lazily
>  would probably break a lot of code/assumptions in the php engine.

Frankly my strong preference would be for on-demand initialization =
because otherwise each page load could end up running lots of code to =
calculate values that are never used on the particular page.

> My preference would be to make it easier to use dynamic expressions, =
and recommend in coding guidelines that
> certain types of expressions "SHOULD NOT" be used for constants that =
vary on a particular host.
> (network calls, time, etc)
>=20
> ```
> const DEFAULT_PAYLOAD =3D json_encode(['key' =3D> 'value']);
> const ALLOWED_ELEMENT_TYPES =3D array_merge(self::FIRST_TYPES, =
self::SECOND_TYPES);
> const ELEMENT_LENGTHS =3D array_map('strlen', self::ELEMENTS);
> ```

You and me both.

-Mike=