How to iterate a collection and have access to preceding item within the loop

I have a collection which looks a lot more complicated than this:

$c = collect([1,2,3])

But essentially I need a loop where I can access both the current item AND the previous one with each iteration. If there is no previous item null will be fine.

I know how to do this a couple of ways but they aren't pretty to look at. One way is to use an old-school for loop with indexes like $c[$i] and $c[$i-1] and the other is map over the collection and pass the item into an external $previous variable at the end of the loop callback.

Anybody know a better way to do this?