There is a lot of magic going on in the Symfony 2 form component, and while this magic is frequently convenient and borderline awe-inspiring, it sometimes has the unpleasant side effect of making it unclear how to do more fine-grained tasks within the form. A standard select list can be created using Symfony’s choice field type; it is pretty clear how to create a new choice field with simple, non-dynamic options (e.g. gender), but it gets a little more complicated when you want to create and validate a dynamically generated choice list.