Now that you’ve read the overview / disclaimer, let’s dive into Facebook.
First off, ensure that you have registered your application with Facebook and have created the following in your settings file:
1) Create the redirect URL
The first step in the oauth handshake is to redirect to Facebook with some application specific data in the URL including your application ID and redirect URL (where you want Facebook to send the user after they’ve approved / denied the application):
2) Redirect to provider’s site
This url can now be used to redirect to Facebook (i.e.
3) Handle the response (approved or denied)
Once the user makes their choice to approve or deny, Facebook will redirect back to your redirect_url. You will need to verify the user approved the application:
If any of the above tests fail, we can safely assume the user either arrived at this page directly (i.e. by typing in the URL) or they denied the application. Either way we don’t want to proceed and should redirect them to the start of the registration flow (i.e.
4 & 5) Get an access token and the user’s profile
At this point the user has authorized your application but you don’t have actual access to their data yet. To get that you’ll need to request an access token. Notice that we’re saving the access token to the user’s session as we don’t want to request it more than once during the registration flow.
Once you have the access token, you can then make the request for the user’s profile data:
That’s it! You can now use the user’s profile information to pre-fill a registration form, perhaps skipping over fields where you already have a required value such as an email address or first and last name. Just be sure to save their Facebook ID along with their profile so you can use it validate them in the future. You should also save the access_token and expires values so that you can make future requests to the API for this user or refresh the access token when it has expired.
In a future post I’ll be looking at how to detect an already registered user as well as provide a login with this provider button.