What is the policy on PHP extensions listed in the symfony components' composer.json? For example, many components of the framework use the ctype extension, which is not included by default in some PHP installations. e.g. on Alpine Linux.

In PR 22676, @xabbuh mentioned that PHP standard extensions were not listed as ext-requirements in the past.

The Symfony Default Distribution's requirements checker lists some extensions which must be available to run the full-stack framework, however e.g. the session extension should not be necessary for CLI-only apps.

Which extensions are considered standard and must therefore be included in a custom minimalistic PHP installation?

Thank you very much!