If you use YAML in PHP, then you had until recently the choice between the C based PECL extension syck or the horrible spyc PHP based implementation. With syck it has the issue that it only supports the core standard and not stuff like merge-key, which is a very very useful extension to the core YAML standard.

He also points out another implementation that the Symfony framework has created - one built around regular expressions (slower, but a "more correct" version).

I've been going through all those open source projects and cutting the dead weight. [...] One of the victims of this review has been Zend_Yaml. Earlier this morning I found an odd comment on the Zend_Translate_Yaml proposal by Thomas Weidner that he was erasing his proposal on the basis that there had been no progress on Zend_Yaml.

He's removed the proposal from the Zend Framework proposal pages after receiving an email noting that the package would not comply fully to the YAML 1.1 specification and couldn't be included. With the introduction of the Syck extension into PECL, it could support it but Padraic opted to just tell the ZF group about this functionality rather than working on the build himself.