Shane did some work on a threads extension available in PECL a couple of months ago. The extension is very experimental.
There’s no plan to incorporate multithreading into PHP5 – if we believe the experts :)
I am not sure about how SRM can help with multithreading. At least it provides persistency across requests which allows to emulate a multithreading environment yourself in PHP (left aside if it’s a good idea e.g. to implement priority management of “threads” in PHP itself and not the Zend engine). Comments are welcome.
What’s missing is a threads implementation similar to Java or Ruby, especially with features like:
– set and manage the priority of threads
– define threads as daemons
– allow for synchronized threads (see Ruby’s Mutex Class)