Michael Dowling has a new post to his site today talking about the work that's being done on the upcoming release of the Guzzle HTTP client. In the post he talks about a major change in how it allows for asynchronous requests and the work on Guzzle-Ring to make it happen.
Guzzle 4 has been out for a little over six months. It has proven to be leaps and bounds better than Guzzle 3, and I've been very happy with the design so far. However, after the release of Guzzle 4, I've received feedback from numerous members of the PHP community that can be boiled down to "Guzzle needs async support." While Guzzle has always had the ability to send requests concurrently using a pool of requests, there was not a way to send asynchronous requests.
After a couple months of work and borrowing concepts from Clojure, I've created Guzzle-Ring, an extremely simple adapter and middleware library for PHP (not just Guzzle) that can power both clients and servers for both synchronous and asynchronous requests.
The Guzzle-Ring reduces the need for the previous complexity of creating multiple adapters, which ended up with the adapters knowing too much about the request itself. He introduces the Guzzle-Ring system that will be included in Guzzle v5, heavily influenced by Clojure. The adapter makes the request as simple as passing in an array and makes use of "futures" to handle the request/response cycle. He also talks some about creating middleware piece that helps integrate it into your application, wrapping functionality inside of another method. He illustrates all of this with code examples and includes others such as fetching of future responses, sending requests concurrently and the Guzzle-Ring server adapters.