Additional features (captcha script, facebook API) for my existing website (PHP/MySQLl)

I run a site were users can arrange to meet to watch a film in a local cinema. Now I want you to further improve the system. Part A: some facebook API login stuff Part B: include a captcha to prevent spam Please see below for a more detailed description. You will get full FTP/MySQL access to the site. ## Deliverables A) - Use the facebook API to log in to the site/Beside this the independent login using my own user database should remain possible. (Is it possible to create a new user with his facebook username in my own database if one logs in using his facebook account for the first time? What do you suggest to have both possibilities login with my database/login using facebook API) - Existing users should be able to connect their facebook account to their account on my site and be able to log in using the one or the other. - If users create new announcements to find an escort I want to post a message to their facebook profile (they should of course be asked before if they really want to post this) B) Spam got a problem during the last months, I therefore want you to include a Captcha ([login to view URL]) preventing spamming in the "send messages dialog".