Yes, I forgot to say something. Like Cleo123 said, I do emphasize on the point that you should always look up functions on the PHP website and see how they work. If you can't find a good explanation, then you've got the forum or google.
Here you've got a lot of sites to start with. Once you get the logic down, things will come smoothly. Firstly, You should do a research about the differences between POST and GET functions and what they do. They can make a big difference in your application as in the data being hidden or shown in a URL address.