When php:version is a list, a dict with settings for different
versions can be added under ini key of cli and fpm:config keys

php:
  fpm:
    config:
      ini:
        settings:
          # global settings
        '5.6':
          # settings for 5.6 only
  cli:
    ini:
      settings:
        # global settings
      '5.6':
        # settings for 5.6 only