The thing which I don't understand is: why do people want backward compatibility that much? For me, PHP6 is the new environment and I don't want to move my existing solutions there. That just won't be right. Just like I didn't reuse code written for PHP4 in PHP5 projects.
This is a major version, so I create new major version of my code. Situation is just the same everywhere. Perl5 vs Perl6, Cocoa of MacOS-X 10.3/10.4/10.5… If ones need to use some older scripts, they can run them using older version of PHP. It is quite common to have both PHP4 and PHP5 installed on hostings these days. Call to developers: Create new versions of your apps/libraries which use new features of language. Make your users interested in upgrading. If users want it, hosting-owners will consider upgrades faster. It's all about marketing ;) -- Alexey Zakhlestin http://blog.milkfarmsoft.com/
