There have been a few requests to provide support for editing YAML Ain't Markup Language files. The support has already been written by Tor Norbye, but was available only for Ruby projects. After discussion with Tor I have moved the YAML support from Ruby to a more general location and from today's builds it is also available in NetBeans PHP distro and in PHP projects.
You can create a new YAML file through the New File Wizard, where you have to choose the Other category and EmptyYAML.yml template.
As you can see from the next screenshot, the support includes not only a template for creating new YAML file, but also features like code folding and coloring. The structure of the file is also reflected in the Navigator window.
Code completion is available in the editor, and a reference card for YAML is displayed in the popup documentation window.