[TYPO3-50-general] Getting all classes implementing a certain interface

[Malte Jansen]

Hi!

Is there a way to get all classes, which are implementing a certain 
interface.
You can get the interfaces from a certain class, but the other way round 
it does not work.
I could not find anything.
It would pretty useful as somekind of hook. Creating objects of a 
certain type over one or more packages.

Cheers,

Malte