Has anyone explored using PHP with a framework -- I'm considering the Yii framework for PHP -- and/or Ruby on Rails?

Could you tell me:

• what you are using it for,
  
• your pros and cons for using either,
  
• easy of use,
  
• the availability of resources for learning and trouble-shooting,
  
• references you highly recommend, and
• anything else you find relevant.

Thank you kindly.

Simone Vuong
Health Studies Section