This one would not be called directly. Session module's object support is tricky...

I came up with better idea. Since we have object, all we have to do is create new one. Currently we have SessionHandler object only and it does tricky and buggy method handling to support create_sid() method.

I'll leave current SessionHandler definition as it is now and create new SessionSidHandler(supports createSid()) and SessionUpdateTimestampHandler(supports createSid(), validateSid() and updateTimestamp() methods).

This way we can keep compatibility with current PHP 5.5 and avoid buggy method handling hopefully. I have to consider well enough before start writing code, though.

SessionHandler object uses "previously used save handler" as it's base. This is clever way. I wouldn't code this like. However,it is tricky and it can cause issues like "parent module is not opened". This feature may be better to be removed in the future...