To create a login screen, you can use PHP forms. However for the backend part like saving user data managing user accont details, you can integrate our App42 PHP SDK. In which we have module name as User Management which helps you in signup/signin, reseting user password, assinging user roles, adding extended profile etc.
Please have a look at this link to get started with it and let us know if you require any help from our side while integrating App42 SDK.
We are happy to help you!!!