MarkR wrote:...Don't worry about that though, supporting PHP4 is pointless anyway.
Mark
It's pointless unless you're writing an application which (a) is targeted for a client who is on a host running PHP4, (b) targeted for general distribution (open source or for purchase) and you don't want to exclude potential users/buyers who happen to be on the significant percentage of servers which are still running PHP4, or (c) any of the other reasons you can think of that it might be desirable for your application to run under PHP4.
Just like a good web designer who wants to reach the widest market for a site will not assume that all users are running IE7 on WinXP-SP2 over a Cable or DSL modem, a PHP developer may not always want to assume that everyone who will want to use his/her program will be able to install it on the latest/greatest versions of PHP, MySQL, and Apache. How backwards-compatible it should be will need to be a case-by-case decision based on an analysis of your expected user base, the current distribution of PHP versions amongst that user base, and the benefits/trade-offs of using functionalities only available in the latest versions versus settling for the use of older functionalities.