PHP is not strongly typed, so it's not a good idea to use scalars of
different types (here it's an integer vs the string 'new') to represent
different possibilities. This can have bad effects when type juggling
occurs, and it's also harder to figure out what the type of the
parameter can be (because a numeric ID might have been passed as a
string). Using integer vs null avoids all of this, and also allows us to
use nullable typehints.
These changes were partly copied from
If981cb35bf19a8469aa6c43c907e107cf8c65bc2 and should help with the
migration to the Filter value objects.
Change-Id: I8837d46c3c33761fea53f67b530b721dc7bd49b0
