Popular WebDAV framework for PHP. Use it to create WebDAV, CalDAV and
CardDAV servers. It supports a wide range of internet standards related to
these protocols. The most relevant are:

* WebDAV
* CalDAV
* CardDAV
* vCard 2.1, 3.0, 4.0 and jCard
* iCalendar 2.0 and jCal
* current-user-principal
* Extended MKCOL
* WebDAV-sync
* CardDAV directories
* CalDAV delegation
* CalDAV sharing
