If you know the basic elements of HTML, you can try to enter into the PHP world.
PHP is a programming language that will allow you to create
interactive pages and to see the results in the web.
If you will be clever, you'll be able to administrate a database, too!
If you already know a programming language, you can easily export the basic concepts in the PHP language.
What are the basic concepts? Not so many: the idea of variable (and of the operations whith it) and the control structures. These are the sequence, the selection and the iteration.
Then, it's enough to change some sintactic rules (but after all, they are very similar in every language!) and you can start!