INDK

First, PHP5 is not "new". Early versions of the Zend2 Engine were available in CVS a very long time ago and were fairly popular to the PHP developer community even before any release of PHP5 was made. If your installation of PHP5 is unstable, I recommend you report it to the Zend Mailing Lists because I think they would be very surprised to learn that PHP5 is unstable.

Second, as far as "Functionality of some functions changed" goes, as someone already pointed out all the compatibility issues are listed here. Now tell me how much of that have you actually used?

"The only major change is the OOP model". RTF ChangeLog.



The natural progression of languages has been something like this: Statement-based languages (ASM, etc.) -> Procedural Languages (Pascal, etc.) -> Object-Oriented Languages (Java, etc.). PHP4 is a procedural language with a very half-assed set of OOP features. PHP5 is an attempt to add some real OOP features to the language (protected methods and member data, interfaces, abstract classes, ...). These are things that true OOP languages actually have.

The real question isn't even really about PHP4 or PHP5, it's about your preference for object-oriented programming. If you want to switch to PHP5, research OOP first (or while you make the transition). This area of software engineering has been so heavily researched that you should be able to be able to find an endless amount of documents that discuss OOP programming in general (there isn't much documentation related to PHP5 itself on OOP, but even reading articles that cover OOP with C++ or Java examples can still be very good at demonstrating the key points).

If you plan on using PHP5 because it's the latest, and not because you want to make use of the new OOP features, then just stick with PHP4 until you understand, and ultimately prefer -- like all the best programmers do -- object-oriented programming.