Best way to learn PHP is to buy a book mate.
I suggest Larry Ullman's PHP For the world wide web. It's a great little starters book with enough information for what you want to do.
TextPad is the best "free" text editor 😉 or PHP Expert Editor.
Just a quick bit of non-techno bable, HTML is used to display text, images etc on web pages, PHP is a programming language which "makes things happen". It's use to enhance HTML (web pages). They are used together.
Good luck 😉