In the DonationInterface changes you made, there are still invocations of the php4 constructor methods in the child classes. This is not a big deal and I can fix that, but I am curious about the motivation behind these changes. The specific files you made these changes in for DonationInterface are 3rd party libraries, and I am hesitant to modify code in them when it's not necessary, so as to facilitate upgrades to the libraries down the line - and AFAIK, PHP5x still supports using PHP4 constructors for backwards-compatibility. Although perhaps this has changed/is slated to change in the future?
A valid concern, feel free to revert any files you don't want changed. This was semi-automated :)
Consistency, is the main reason. Second reason is they've already broken PHP4-style constructors if you happen to use namespaces (see 5.3.3 release). We don't, but I feel it's a picture of things to come.