Facebook Sign up and Sign in on CakePHP Website

I want to do sign up with Facebook and Sign in with Facebook on my cakephp website.Previous developer already completed 70% of the work but faced the below issue.'Everything work fine but when I acces I want to do sign up with Facebook and Sign in with Facebook on my cakephp website.Previous developer already completed 70% of the work but faced the below issue.'Everything work fine but when I access in controller then it shows error that Facebook class is not access.'I need a developer who can complete the job in 24 hours.