php 7.4 "immutable classes" support

[Xon]

php 7.4 plans to include preloading classes, which are then rendered immutable.

This feature will strongly impact XenForo 2's class extension framework, as preloaded classes can not be re-declared which limits pre-loading add-on classes

PHP: rfc:preload

wiki.php.net

Preloading is going to be controlled by just a single new php.ini directive - opcache.preload. Using this directive we will specify a single PHP file - which will perform the preloading task. Once loaded, this file is then fully executed - and may preload other files, either by including them or by using the opcache_compile_file() function

Preloading Limitation
Only classes without unresolved parent, interfaces, traits and constant values may be preloaded. If a class doesn't satisfy to this condition, it's stored in opcache SHM as a part of corresponding PHP script in the same way as without preloading. Also, only top-level entities that are not nested within control structures (e.g. if()…) may be preloaded.

One of the reasons I want to bring this up now, is that the code_cache system could have some relatively small changes to support the contents being "preloaded" and then loading changes with new filenames/classnames.

I'm not sure how easily the class extension system could be adjusted to being automatically pre-loaded