On the Northclick blog, Soenke Ruempler has posted an update on the "message queue" project based on a previous draft.
Some time has elapsed since we wrote our draft for a message queue system written in and for PHP. Now it's time to give you guys an update and working beta-code. [...] You can find the project homepage at https://opensource.ruempler.eu/pmq/. We'd be proud if you have some cool naming tips for this project - we haven't registered a domain yet. At the moment it's temporarily called "PHP Message Queue".
Check out the post for more specifics about the updates/advancements they've made or you can download the current code from their SVN repository.