Trying to summarize this discussion... I think we can all agree that the main problem is "code duplication for array access when parameters are possibly not existing". I think we all can also agree that @ can be both used properly and misused - and it is a blunt tool and not a nice solution to the previously stated problem.
Some suggested that the ternary if comparison should suppress the notice automatically. This would break existing code and also be confusing since people expect a ternary if and normal if to work the same way. Some suggested ?? as an array access operator that suppresses the notice and has 3 variants: A: nothing specified - uses null as default, B: has default specified, C: returns X if index exists or Y if index doesn't exist. This effectively solves the code duplication problem and is a shortcut for saying "the array index may or may not exist". One person said that the relation between ? and ?? and == and === would make the operator non-intuitive. Other people disagreed and claimed the opposite. So basically the discussion now is what exact characters that should be used to represent this operator? I really hope we can get this implemented quickly... I worked with $_POST yesterday and I could really use that ?? operator. ~Hannes