Before picking between HTML and PHP, you must first know what you want to do. If you are making a regular web page and your main function of your web page would be to display content, pictures, videos, styled text, etc., you will be best off using HTML.
If you want to do more than just display content, such as gather user information or create forums, you will need to use PHP.
What's the difference?
HTML is a display language. All it can do is show things. It cannot receive information or change at all once it's been created.
PHP is a full programing language, which allows for an almost limitless ability to create. In fact, PHP can even write HTML code to display the information it collects. But there is one very good thing about using PHP and that is that you can use HTML when writing it and it will respond just like HTML.
If you think you may need to do more than display content, PHP is the way to go for quicker design.