Since the PHP group announced they weren't going to support php4 any more when 2007 ends, I have been watching with amusement the reactions this fact has sparked. In general, it feels quite similar to previous public announcements of product discontinuing, such as Windows 98, or Firefox for windows 98, etc.
The most absurd reactions come from very angry people which not only demand support for that product to be extended indefinitely but also do not use the product at all or do not have any decision power about the use of that product in their organisation or environment. They can fill in pages and pages writing infuriating comments about how evil is vendor X for not supporting product Y, and how bad is it for everybody, without giving any solid reason usually.
And the rest of the blame is equally distributed amongst sys admins and developers. Sys admins say they can't upgrade to php5 because the applications running in their systems are not designed with php5 in mind. Developers say they can't develop for php5 because their sys admins do not offer support for php5.
stop blaming each other.
It's not that hard to migrate an application to php5, unless it's a complete disaster. For instance, I saw one which had some functions named public and private. Honest! Those functions were repeatedly called thorough the whole code base. Obviously when trying to run this with php5, it failed spectacularly. (Somebody tried to fix it replacing every public with pub and private with priv, and then it broke other parts of the application, but that's another story...)
Personally, I wished every host in Earth had moved to php5. I never use php4 in my projects and it's really annoying to have to downgrade the code for distributing it publicly. It also breaks my heart to have to emulate some php5 functions when working with legacy php4 code for php4-running servers, such as for example array_combine.
And at the end I wonder, can we take seriously a developer or a sys admin which have not learnt about php5 yet, even if it was released more than three years ago? I can't.