PHP App Change for LinkedIn Authentication

I have a web app (in development) that I want to modify the logon and signup functionality as outlined in the attachment. Essentially, we have 2 types of users (A and B). All A users will signup and logon using LinkedIn authentication and OAuth2. All B users will signup and logon using the existing application functionality. We will remove all references to Google+ and Twitter logon functionality. This should be a very easy change for an experienced PHP developer. The underlying database is Postgres. To demonstrate that you've read these requirements please put 'PHP Mod' in your response. All responses without 'PHP Mod' will be deleted. I will provide more details about type A and type B to the freelancer selected and will provide the LinkedIn application details and recaptcha link needed.