On Pàdraic Brady's blog, he talks about some thought he had on a YAML component for the Zend Framework and some of the feedback he's gotten so far.

Since I'm used to the format from Ruby and Perl and since it's used for a similar purpose in the PHP Symfony framework, I also suggested using YAML configuration files since they are far more readable than XML and remain machine readable. I believe this went over quite well. Later on I realised the Zend Framework has no YAML support, and after some searching noticed the only (apparent) PHP parser was the Spyc library

So I fired off a few emails to the fw-general mailing list of the Zend Framework to see if there was any interest. I'd like to thank Matthew and Gavin for their feedback and I've since decided to have a go at implementing a YAML parser in PHP.

He notes that there is already a YAML parser for PHP5 (Syck), but that creating one for the Zend Framework is a different animal. He finishes up the post talking about where to start with the parser, what it is, and the next steps for him in its development.