Today vfsStream 0.10.1 has been released, containing two bug fixes. The first was a problem with the vfsStream::create() functionality introduced with 0.10.0, where using numeric directories failed because of implicit type conversions (in PHP) and explicit type checks (in vfsStream). Thanks to Mathieu Kooiman for finding this issue and providing a patch.
The other fix is a mix of a documentation and type hinting fix: now you can only use directories as root instance - before it was allowed to add files as vfsStream root with with vfsStreamWrapper::setRoot(), however this failed latest when trying to access other files with a directory name. Starting with 0.10.1 you can not add files as root any more, and this was also used to change the return type documentation so you can get better auto completion when retrieving a directory object with vfsStreamWrapper::getRoot(). Thanks to Dmitry Kabanov for reporting this issue.