Hi internals Libxml is used as the underlying library for many PHP extensions. Interestingly, libxml can be built with supports for various features disabled. E.g. you can build libxml without XPath, Schemas, HTML, ... support. In that case, these features are unavailable in PHP. E.g. some classes may not be defined or functions may emit a warning instead of performing an action.
I'm thinking of proposing an RFC that puts stricter requirements on libxml at build time. That would make such features a requirement during PHP's build process. This will simplify maintenance and will also make sure that users can rely on these functionalities to always be available. Please let me know what you think. Kind regards Niels