The Horde project released the second PHP PEAR package representing a small subpart of the Kolab functionality within the Horde framework: Horde_Kolab_Server.
The package allows to access the Kolab LDAP database. Some examples are being given on a page in the Kolab wiki.
The package is the second in a series of five packages that will be released over the next few months. The full set of packages will allow you to easily deal with data stored on a Kolab server within your own web applications.
In addition the Horde_Kolab_Format-0.1.1 has been released. This is a bug fix release.