While it is most typically touted as a fully-featured shopping cart system, Magento is an awesome framework to boot. Of particular awesomeness is the layout system. In essence a page is created from "Blocks" which all inherit from an abstract class which does not assume the use of template files. These blocks are assembled according to a layout which is the composition of a bunch of XML files being merged together to describe a hierarchical structure of blocks for each page (inheritance supported for DRY). I love this system but Magento is a very heavy framework.
Are there any other frameworks which use a similar system? I.e. layouts that are defined outside of the template files as described above. PHP 5.3 is preferable but would consider frameworks in other languages.