I was curious about how often PHP is review for updating. The current version on DH seems to be 5.1.2, while the currently release version is 5.1.6. 5.1.2 was released way back in January…;).
As expected with the first few 5.1 releases, there have been changes. A number of PHP applications/libraries are now carrying a minimum 5.1.4 requirement. The Zend Framework does, for example.