How to remove .php extension only for pages under a sub directory?

I am trying to remove .php extension for only pages under a subcategory folder of the website.

currently: example.com/blog/my-first-blog.php

what i want: example.com/blog/my-first-blog/

I have tried the following rule in .htaccess (placed in root) but it still shows .php

RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{DOCUMENT_ROOT}/blog/$1.php -f
RewriteRule ^(.+?)/?$ /blog/$1.php [L]

Answer

I figured it out I just had to create .htaccess file under the “/guide/” directory. with the following rule note RewriteBase /guide/ for making sure it only removes .php under “/blog/” folder

RewriteEngine On 
RewriteBase /blog/
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^(.*)$ $1.php [NC,L]