Authentication url redirect to login page

[msyadav88]

I have made setup of php oauth2. But when I try redirect to the auth_url ( got from getAuthenticationUrl() ) , It redirect to the login page of wordpress site ( http://v2.iregister.ie/wp-login.php ) .
Is admin login is mandatory to get the authentication code ?

[msyadav88]

I read in articles that if the user is not logged in the server then it will redirected to the login screen.
I am trying to do all this process dynamically so is there any way to do all this process dynamically without doing login manually?
Or I think the other option is to authenticate using client credentials. Can you provide me with any demo example of client credentials?