If you use SQL Power Architect, you know it is one of the most versatile open source schema and Entity Relationship Diagram editors out there, with built in functionality for Pentaho’s Kettle and Mondrian tools. I also develop Symfony PHP projects and needed to use their export functionality to convert their xml schema files into a yaml schema. It’s still a work in progress, but there is a working xslt template for Doctrine export. Try it out and let me know what can be improved or modified.
YAML Schema Exporter Project (GitHub)