I'm pretty experienced in development in general, and also did some PHP coding to generate hmtl pages. I've also got a running WordPress blog with a number of posts.
As a start, I want to "generate" the index page (the first page the user sees when coming to my domain). I can probably code that in PHP, but I'm not sure where to "put" this PHP code within my WordPress site. (I want to re-use the general design of the site.) Later, I want to have other "types" of pages that I generate in code (e.g. a user form and - based on the input - generated result pages).
Probably a totally noob question ;-) but I'd appreciate any pointers (also blogposts, books etc.). Thanks!