On the Graze.com Tech blog there's a recent post about sharing logic between controllers with the help of traits. He makes use of the traits functionality in PHP to abstract out functionality common to multiple controllers (in his case, common user functionality).
There have been a few times I have come across a situation where I need to share some logic between controllers but it hasn't been as clear cut as abstracting that logic out into a library. I've been pondering the best way to tackle this problem and would like to share my thoughts.
In his example he shows how two different controllers, the Account and Signup controllers, both need to be able to look up an address and perform some simple checks on the results. The logic is duplicated so he first tries to move it out to an abstract controller but notes that it's not the most ideal solution. Next he tries moving the code out into a library but finds issues with separating out the necessary concerns. Finally he moves the logic into a trait (AddAddressTrait) that contains it and allows the direct integration of his "lookupPostalCode" method into the controller without inheritance or other design issues.