php and html coding for dynamic webpages.?

[andrew m]

Hello all, I have a question on php and html coding, im curious on how to make my site a little more dynamic instead of programming each page. I know some sites in their url use PHP, and CSS. Now I know a little php, but CSS is no problem to me. My site already contains some php but its within the html file, what I want to know is how do I take the php out of the html file and just have a php file, where the html will pull the php information. I have seen a tutorial on how to do this but now I can't seem to find it anywhere. Basically what I'm looking for is say my site is www.example.com and someone goes to the about page, they are also logged in to their account. so lets say www.example.com/about.php?user=username. so now that page is tailored to them. Now what I currently have is a page that a user could login and they go to this about page so if you are still following me we are at www.example.com/about.php. Now I have a few links on that page, and I really don't want to make a whole new page so I would like when the user clicks a link say the link is settings it will take the user to www.example.com/about.php?settings. I have the css style sheet setup and I know how each page is supposed to work but I really don't want to have to create a whole new page. If anyone know what im talking about and can provide input please help. I know I can be a little hard to understand if you have questions let me know I will try to clarify as best as i can.