\Symfony\Component\DependencyInjection\ContainerInterface contains the following constants:

constEXCEPTION_ON_INVALID_REFERENCE =1;constNULL_ON_INVALID_REFERENCE =2;constIGNORE_ON_INVALID_REFERENCE =3;constIGNORE_ON_UNINITIALIZED_REFERENCE =4;

The documentation for their usage withget() is nowhere to be found. I tried looking for their usage in the Symfony code, but deciphering what they precisely do (and what's the actual intention of using them) is rather hard.

Maybe we should document that?