In a new post to his blog Chris Jones talks about the "gathering momentum" that's forming around the push to the next PHP release, PHP 5.4, including discussions on mailing lists and IRC.

Discussion on the PHP mail lists and IRC channels in the past few days has been looking positive about an alpha release of PHP 5.4 soon. This will be taken from the "trunk" branch of PHP. The exact feature list is under discussion but the mood seems to be "ship what we currently have" though a couple of features are slated to be deferred until later.

He specifically mentions this mailing list post and the emphasis he puts on testing the code. If you'd like to get involved, you can subscribe to the mailing lists here.