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Subject: Re: [PHP-DEV] [PHP-Dev] Versioned Packagers (Iteration IV)
In-Reply-To: <CAEUnE0eEjsBXmz8AEVG1SKE=i08-9dit1ze1K0mWrdyQt4okqQ@mail.gmail.com>
Date: Fri, 5 Jul 2024 11:22:58 -0700
Cc: PHP internals <internals@lists.php.net>
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To: Michael Morris <tendoaki@gmail.com>
From: dusk@woofle.net (Dusk)

On Jul 3, 2024, at 17:16, Michael Morris <tendoaki@gmail.com> wrote:
> Can PHP support multiple packages without rewriting the whole engine?  =
I think so, but it isn't trivial, and the side effects need to be =
cordoned off so that those who need this complexity can have it while =
the beginning and intermediate coders can ignore it just like they =
ignore strict comparison operators and strict typing unless a library =
they are trying to use foists it on them.

I think that focusing on the syntax and tooling for executing these =
imports is starting at the wrong end of this problem. The bulk of the =
work for this feature is going to be whatever engine changes are =
required to support versioning, not the tooling around it.

To that end - consider the following. Let's say that two different files =
in your project import different versions of package Foo. Foo contains a =
definition of the FooBar class, and contains functions which return that =
object.

1) If $foobar is one of those FooBar objects, what does $foobar::class =
return? Is it the same as the fully qualified name of FooBar (e.g. =
"Foo\FooBar")? Does the result differ depending on what file contains =
that code?

2) What happens if you try to pass that string back to something like =
new $class() or construct a ReflectionClass for it? Does that depend on =
the location of the call? What if the call is through something like =
PDO::FETCH_CLASS which occurs within the runtime?

3) Within Foo, would it be true that if $x =3D new FooBar(), then =
$x::class =3D=3D=3D FooBar::class? Does this differ outside Foo (with an =
appropriately qualified name for FooBar)?

4) If those two files both create FooBar objects of their respective =
versions, what happens if you try to pass one of those objects to a =
function in the file using the "wrong" version of Foo? Does it pass type =
checks, and what happens if it does? If not, how does the check fail?

5) What shows up in the output of functions like get_declared_classes()? =
Are there multiple instances of FooBar in there for each version? How =
are they distinguished from one another?=