Parameters as array in Yaml in Symfony2

Try this

parameters:
   array_name3: 
      - [1, 2, 3]
      - [a, b, c]
      - [x, y, z]

Or if you want to have it associative:

parameters:
   array_name3: 
      1: [1, 2, 3]
      2: [a, b, c]
      bla: [x, y, z]

Or if you want more – read documentation