[RFC] [Discussion] Add bundled user_cache extension

Hi internals, This is a follow-up to the previous "OPcache Static Cache" discussion. I have written a new RFC and implementation. It addresses the issues raised in the previous thread, drops the parts that led to feature creep, and moves from OPcache integration to a new bundled user_cache extension. (The OPcache User Cache entry in the commit history is a remnant of a completely new implementation built from scratch. After realizing partway through that it wasn't necessary to depend on OPcache, I separated it.) RFC: https://wiki.php.net/rfc/impl_user_cache Implementation: https://github.com/php/php-src/pull/22730 The scope and API have changed a lot from the previous proposal, so I am starting this as a new RFC with its own discussion period. Because of that, I am not sure it can make the PHP 8.6 feature freeze. If the release managers think 8.6 is not realistic, I will target 8.7. As mentioned in the previous thread, I think library developers would benefit from having this available sooner, so feedback is welcome. Best regards Go Kudo