Have made some limited progress - integrated the fields and can test validity of secret and otp, but I'm still having difficulties trying to intercept the login process, i.e. before I get into the administrative area, I would like the function to verify that the secret and otp is correct as well.
Or to have "Continue" to redirect to 2FA page for further processing. Can't find where to edit, unfortunately.
Have integrated PhpGangsta's Google Authenticator library and basically, this works on its own.