How to build an application in PHP without using a framework?

I read a few books that taught me how to program in PHP. I know OOP, and I want to create an application using it. But how should I organize my files and folders ? How do I know what pattern I want to use while programming ?

I don't want to use a Framework, as this is going to be my first project. What are your techniques ?

I have to say that I'm a bit frustrated because I spent months teaching myself PHP and now that I feel comfortable with it I don't know how to build the site !

Thank you.