cakephp/cakephp — comment on commit b4faa00703d45567d714122930bdd3a96ad3663c
File: lib/Cake/Model/Model.php line 2821
By markstory:

I think being able to provide a custom parent_id field makes sense, we should still trigger an error if someone asks for a field that doesn't exist. As for the isset() in the loop, it could probably be moved out and done once for sure. I don't know why I didn't think of that earlier.