Initializing objects from other objects in PHP

Sometimes we need to initialize an object based on another object. Typically, if we have a class MyClass and subclass MyExtendedClass with some additional functionality, we may need to turn a MyClass object into a MyExtendedClass object. How to do that easily in PHP?

Dokuwiki Shibboleth authentication backend

DokuWiki is a standards compliant, simple to use Wiki, mainly aimed at creating documentation of any kind. It is targeted at developer teams, workgroups and small companies. It has a simple but powerful syntax which makes sure the datafiles remain readable outside the Wiki and eases the creation of structured texts. All data is stored in plain text files – no database is required. (description taken from DokuWiki homepage).