[1llusion]

I'd really suggest you first to do some smaller projects. Have a project just about log-in and user management. Then project just about video streaming etc. Divide it into smaller projects and once you are comfortable with these projects, you can merge them into one big (not copy/paste, but you can be inspired by them).

Have a look at sessions: http://www.w3schools.com/php/php_sessions.asp they should help you. After that, read some articles about secure log-in methods etc.