[RFC] Namespace-scoped declares, again

Hi internals! Some time ago I introduced the following proposal for namespace-scoped declares: https://wiki.php.net/rfc/namespace_scoped_declares The idea is to allow specifying declare directives for a whole library or project using: namespace_declare('Vendor\Lib', ['strict_types' => 1]); I've finally gotten around to implementing this proposal ( https://github.com/php/php-src/pull/2972) and would like to move forward with it. The reason why I'm picking it up again is some feedback I received for the explicit call-time send-by-ref proposal. The main objection seems to be that the feature has limited usefulness if it's optional rather than required, because you still can't be sure that something is a by-value pass, just because no & is present. At the same time, we can't make this required anytime soon due to the large BC impact. Namespace-scoped declares are perfectly suited to resolve this problem. We can introduce a require_explicit_send_by_ref declare directive to make the call-site annotation required, and libraries/projects can easily opt-in to it using namespace_declare(). There would be no BC impact, while at the same time projects could benefit from the additional clarity and performance improvements immediately. Thanks, Nikita