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Date: Fri, 30 Aug 2019 20:56:43 +0200
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To: Chase Peeler <chasepeeler@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Bringing Peace to the Galaxy
From: andreas@dqxtech.net (Andreas Hennings)

On Fri, 30 Aug 2019 at 19:38, Chase Peeler <chasepeeler@gmail.com> wrote:
> On Fri, Aug 30, 2019 at 12:39 PM Andreas Hennings <andreas@dqxtech.net>
> wrote:
> > The only way to make this possible is to either deny all progress, or
> > to make a distinction on file level (or "package level", whatever that
> > means).
> > So, opt-in BC breaks.
> >
> That's not true at all. There are a ton of things that have been discussed
> that will progress the language and don't require any sort of BC break.
> Union types is one example. Support for Enums is another.
>
> Even if a BC break is required, it's not automatically a bad thing. Whether
> we are looking at plugging up a big security hole, getting rid of/modifying
> a rarely used feature, adding support for something that it's currently
> impossible to do, or just doing something that adds tremendous value to the
> language. In all of those cases the impact of the BC break should be
> weighed against the benefits.

The problem and trade-offs I am describing are already impacting me today.
I am working on a Drupal 7 site with lots of legacy code, and I am
developing Drupal 7 contrib modules that I want to be available to a
large audience.

In one of these modules I initially used the ?? null coalesce operator.
Then I had to replace all of the instances of ?? with the more verbose
old-school code, to make it compatible with older PHP, because there
are still enough Drupal 7 installations out there which have not
upgraded to PHP 7 yet.
I also had issues with old 3rd party libraries, which stood in the way
of PHP version upgrade.

In a world with "editions" per file or per package, such projects
could more easily use the newest PHP version, while the old libraries
would continue working.