Add html div tag based on file name

Sorry if this is a nooby question, but I have the following problem: I have some sort of a Documentation as a multiple webpages. I created a basic navigation bar on the left of the screen using a tutorial... To be able to mark the active link every page has its own unique navigation adding it's own link to a specific div class. The problem is that if I wanted to add another page to my collection I would have to add the link in every html document. I know that there is a possibility to include other pages Php code to have one navigation document, but I have no idea on how to achieve that the current page is getting highlighted. I would appreciate any help.