CMS to manage pages on a website(building one). What are good and bad practices?

I hope this isn't the wrong place to ask this question, but this one is webdev related but not a question regarding code itself.
I want to build myself a CMS which I could later use to manage webpages on websites. My question is not about which CMS to use, but about how to build one myself.
I am in what you'd call the planning phase and my current concern is related to wether or not it would be a good idea to have the pages stored in the database, and work just like an article page would, as in include the header to get the style elements and just use the code stored in the "pages" table which will be generated according to what page capabilities would be added, or each page could be stored as a table(with elements like body, sidemenu, header) being the columns of the table.
The other option I can think of is physically writing the webpages in the directory as a whole using php i.e. .

TL;DR: Is using pseudo-pages stored in the db a good idea or should I write them in the http directory?

I want to mention that I tried looking for an answer to my question but I guess I just don't have the knowledge about how an where to look for structural advices for a CMS.