symfony - Link several form fields to a single entity field -

i have following problem:

i'm using symfony 2.0 (it's intended upgrade 2.3 it's released). write program managing library , give user separate input fields every author of book. in end, authors should saved in single database field.

i tried using custom form fields, cookbook tells me, couldn't figure out how it.

best regards, grimreaper1908

---------edit----------

thanks cerad's answer, solve initial problem. unfortunately, have modify solution in such way, can distinguish between forename , surname. in end, data still should saved in single database field. can use collection within collection? if that's not possible or wrong approach, maybe has idea of how it?

best regards

basically, want add get/setlistofauthors book entity returns/accepts array of authors. use form collection field.