Facebook login to my website + improvements to DB

I would like this done predominantly in PHP. Exactly like the login page for This website Freelancer.com, i want users to either register manually (I have already coded that as working) or "Login with facebook" When they login with facebook, my understanding is that it will: - Check if they are already logged in, if so take them to a members only area on my site. - If they are not a member, they will approve what my app can access from their profile - it will then take these details from Facebook and insert them into mySQL database for members I would like they facebook profile picture to be their avatar on my site, this should appear in the top right hand corner once loggedin. I will also need a "forgotten password" button and page where they can reset their password. I need all the code fully commented to explain how it works, as going forward i will be making minor modifications myself. I already have hosting and can setup FTP access to allow you to work on this. This website is in development and runs from a mysql database, i would like someone with experience to have a quick look over this as well and suggest any minor improvements that could be made.