Based on some of the responses to his previous open letter to the PHP-FIG (Framework Interoperability Group), Anthony Ferrara has posted a follow-up explaining some of his points made and the caching proposal in a bit more detail.

A few days ago, I wrote An Open Letter to PHP-FIG. Largely the feedback on it was positive, but not all. So I feel like I do have a few more things to say. What follows is a collection of followups to specific points of contention raised about my post. I'm going to ignore the politics and any non-technical discussion here.

He points out that while the previous post wasn't completely about the cache proposal (it was used as a "literary device") there was some confusion on it. He walks through the "unnecessary complexity" he sees with it, citing code examples, and makes points about performance, memory usage handling stampede protection and the creation of standard ways to avoid it. He ends the post with a look at group invalidation handling and two ways it could be accomplished, either via namespacing or through tagging the items and using that as a reference point for the invalidation.