Aded Data Helper and Session Helper

These are two objects I find myself using a lot. I feel like the Class Name "Data" might be a bit too generic and would advise an alternate name, nothing came to mind right away.
That is the behavior I expected. isset returns false, becuase foo = null. Also, not that it's important to this topic but there's a dupe, echo "does bar exist? ", array_key_exists('foo', $things), PHP_EOL;

bar is checking for foo.

So, I guess the real question is, if the array_key_exists and is_null, do we return it as null, or send back the $default?