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Date: Mon, 24 Nov 2025 10:56:54 +0200
Message-ID: <CAMW7n8AhbBawCBtfNJZ6XzFSvwhtZotfgBmb1O4CDZ+J2jxt2w@mail.gmail.com>
Subject: Re: [PHP-DEV] [VOTE] True Async RFC 1.6
Cc: internals@lists.php.net
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From: edmond.ht@gmail.com (Edmond Dantes)

I forgot to add an important point.
If a coroutine can be started with its own separate Globals state,
this means there is a technical possibility to safely run coroutines
in applications with global state, guaranteeing they won=E2=80=99t break
anything.

If the rule of having zero Globals becomes the default rule for
starting coroutines, it makes PHP potentially less dangerous.
It means that data can be passed into a coroutine only explicitly at
creation time, and in no other way.

Of course, we need to consider the potential performance impact of
this logic. But if the performance drop is minimal, this feature could
potentially make the language better and essentially turn PHP into a
language where global state doesn=E2=80=99t exist at all. \
After all, any code is code running inside a coroutine.
That means `$GLOBALS` effectively no longer exists. Memory is always
localized to the execution context.

This property potentially allows coroutines to be moved between
threads in the future, because the memory model begins to look like an
isolated region that belongs to the coroutine.

At the same time, this property **does not break existing code**,
because everything remains 100% functional inside a coroutine.
But now we gain the ability to run multiple instances of WordPress in
a single PHP thread, if we adjust the startup code.

All of this resembles Erlang and sounds a bit crazy for a PHP
developer, but so far I haven=E2=80=99t been able to come up with a
counterexample that would make this property negative.

Let me repeat the conclusions:

1. Each coroutine has its own GLOBALS/Static, and a developer cannot
pass global state into a coroutine.
2. This forces the developer to pass objects explicitly, because there
are simply no other mechanisms available.
3. `static` caching breaks for coroutines. But since coroutines don=E2=80=
=99t
currently exist, this is not a problem. Developers will just need to
account for it.