How to build a Social Networking Site from scratch?

I currently have knowledge of HTML and CSS web coding, but I have little understanding of how to create a site where users can register, create an account, log in and out, manage their account, upload fotos, and communicate with other members. I want to create a basic site like this from scratch but I have don't really know how to do this. I have heard of PHP and MYSQL coding but it seems really complicated and hard to understand. I was wondering if anyone knows where I can easily learn PHP and MYSQL and develop a site using that... or if someone knows an alternative method to doing this.