You're running Wampserver (64bit) and you are asking us how to upgrade PHP?
This seems more like a question for Wampserver forums.
The only way that I would know how to do that would be to upgrade Wampserver.
I do not run pre-packaged together software like that ... so normally I just upgrade PHP the old fashioned way. By downloading it, and throwing it on the server.
Doing a quick google for "wampserver how to upgrade just php" returns this:
http://blog.astemplates.com/change-php-version-wamp/
Maybe that will help you.