Native DOMDocument extension
In v3, a Facade was implemented to reach 100% compatibility with W3C's specification.
In this v4 release, we see a drop of the Facade to go back to a native DOMDocument extension. This is because the native libxml bindings are extremely performant, and plain PHP simply can't compete. We used the existing unit tests to ensure there isn't any regression in functionality, but there are certain new quirks due to the libxml implementation, clearly documented in the README.