for modular installations this type of feature is critical. The alternatives are the code you see produced in *nuke type cms system. I really leaves php lacking

I had to change my developement tool due to lack of the possibility to create dynamically loadable (php) modules (with php).  PHP just could't do what I wanted.  Just as Kevin said, this is critical feature in modular systems.

Possible (even though not particularily good) workaround is to "register" (put them in say global array, which maps class/function names to filenames) your "dynamic libraries" where you would normally want to load them.  Then where ever you want to access dynamically loaded classes/functions, first include file containing it/them.

This works only when you don't really _have_to_ access global namespace.  I used this approach on a system where config files scattered all over the filesystem (like apache's .htaccess) can locally change behaviour of my system and add features (register new "handlers" etc).  Instead of actually loading these configs only register new features and loading is performed only when I need to instantiate a "dynamically loaded" class.

This bug was submitted about a year ago, but no any developer comments are still available. According to comments, added by other PHP programmers - this feature is quite important. 
 Will we ever have a chance to know if such funtcionality is planned for implementation?

This is technically almost impossible without rewriting the whole engine.

> This is technically almost impossible without
> rewriting the whole engine.
Now after two years: same situation for PHP5? I could really use something like this (also for a more modular system).