WebLike

Greetings beloved Gurus! I would like some advice on how to go about creating a PHP registration/login system that grants access to all services on a website that has various sections, much like Google; e.g. I have got a Gmail account and subsequently been granted access to all of Google's services like Blogger, Youtube etc. Now I would like to do the same with my website, and grant the users access to all the services with one account registration. I am fairly new to PHP, I have only been tinkering around with it for five months now. I hope my question is not ambiguous or too broad, I need help with how I should approach this, so any pointers with regards to the structure of the database, frameworks, resources, and anything I should take into account would be much appreciated. I am ready to jot down your suggestions. Thank you!