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.
I also, notice that you are calling local methods using static::method(), do you prefer that to self::method(). Not sure if there's a need for static::method() in a no dependency library since there should be no late static bindings. Unless you foresee users extending these classes in such a way.