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Thread-Topic: Planning an RFC to allow calls to global functions in constant
 expressions 
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Date: Sat, 1 Feb 2020 23:00:21 +0000
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Subject: Planning an RFC to allow calls to global functions in constant
 expressions
From: tysonandre775@hotmail.com (tyson andre)


Hi internals,=0A=
=0A=
I have a working implementation for calling global functions in constant ex=
pressions at https://github.com/php/php-src/pull/5139 =0A=
(see PR description for more details, see tests for how edge cases get reso=
lved)=0A=
=0A=
If there was interest, and no implementation or process blockers I was unaw=
are of, I was planning to set up an RFC with votes along these lines:=0A=
=0A=
1. (Primary) Yes/no for supporting calls to global functions, with or witho=
ut the below limitation (requires 2/3 majority)=0A=
2. (Secondary vote requiring 2/3 majority to allow calls to all global func=
tions) Support calls to any user-defined or internal global functions, not =
just unambiguously resolved calls to the deterministic, side effect free on=
es that are guaranteed to be installed in core extensions.=0A=
=0A=
Alternately, have a first vote on allowing a small subset of global functio=
ns calls, then if that passes, start a second vote on allowing all global f=
unctions.=0A=
=0A=
For example, allow `\count()`, `\strlen()`, `\array_merge()`, and `\in_arra=
y()`,=0A=
but don't allow functions such as=0A=
`\strtolower()` (different in Turkish locale),=0A=
\sprintf() (Depends on locale and  `ini_get('precision')`, but so does `(st=
ring)EXPR`),=0A=
`json_encode()` (The `json` extension can be disabled),=0A=
or calls which aren't unambiguously resolved with `\` or `use function`.=0A=
I'll assemble the list when writing the RFC.=0A=
https://github.com/phan/phan/blob/2.4.8/src/Phan/Plugin/Internal/UseReturnV=
aluePlugin.php#L190=0A=
has a list of candidate functions (non-deterministic ones such as rand() wi=
ll be excluded).=0A=
=0A=
I mentioned this earlier in https://externals.io/message/108238#108238=0A=
The use case I have in mind is different from what was mentioned there,=0A=
and this is *just* adding supports for function calls by name, not any othe=
r expressions (variables, properties, methods, etc)=0A=
=0A=
Motivation for the voting structure: There are many opinions on what a cons=
tant *should* be used for, e.g. one opinion is https://externals.io/message=
/108238#107992=0A=
=0A=
=0A=
> Off the top of my head, I can think of three types of things that you mig=
ht call "constants":=0A=
> =0A=
> 1. A value that will never change, and you just want to give a name to. F=
or instance, MINUTES_IN_HOUR=3D60=0A=
> 2. A value set at compile-time, to hard-code a particular condition. For =
instance, DEBUG=3Dfalse=0A=
> 3. A value which is set at run-time, but happens not to change during the=
 course of the application, so should not be over-written.=0A=
>=0A=
> PHP's constants are designed primarily to be type 1 - they are literal=0A=
> values, hard-coded in the source. Unlike C, there is no standard=0A=
> pre-processor for PHP, so type 2 is rarer, but it's possible to=0A=
> implement by manipulating the source file before deployment, or even=0A=
> when running the autoloader.=0A=
=0A=
Thanks,=0A=
- Tyson=