symfony/symfony-docs — pull request #783 by wowo (2011-10-19 08:08:17+00:00)
Title: Field reference attr option added

I've added this to docs, because it ain't documented at all, but is important IMHO. More about this problem here: http://blog.sznapka.pl/how-to-add-a-custom-class-to-form-field-in-symfony2/