How to redirect page with htacces with URL parameter

Question

I have a folder in which HTML pages are saved. I am including these pages with PHP include function. I am calling these pages in index.php with URL parameter value, where URL parameter xpage is equal to page name that are saved in my another folder & index.php is saved in root folder.

How I redirect to 404 page with htaccess if parameter xpage value named HTML page not found in that another folder?

http://example.com/about-me Where about-me is the name of page which is exists in my another folder as about-me.html. I want if this about-me.html doesn't exist in folder then redirect URL to URL http://example.com/404

I also want if url parameter is welcome,home and index then remove it and go to main domain http://www.example.com

Answer 1

It would be helpful if you included some code, but I will make a guess

you don't need to use .htaccess for this

<?php
$file = "somefolder/" . $_GET["urlparm"] . ".html";

if ( file_exists( $file)  ) {
   include_once( $file  );
} else {
   http_response_code(404);
   include_once('somedefault404.php'); 
   die();
}