PHP避免直接访问公共文件夹中的内部php文件

I'm redirecting to the same page index.php via .htaccess everything that looks like this:

mysite.com/something/somethingelse/blahblah

Which means: url's that don't exist. That way, requests like

mysite.com/includes/js/script.js

Are still accessible.

But I would like to avoid access this way:

mysite.com/includes/php/dostuff.php

So I would like to know if there is a method I could use to check in dostuff.php that the file is being accessed directly and not via require.

What I have thought so far is to check $_SERVER["REQUEST_URI"]. But I'm a little lost about what to do from there.

I think it can be done easily checking if a variable exists. So in dostuff.php and similar files there will be this line at the top:

if(empty($myvar)) exit;

However, that won't work on internal files called via ajax. So I still need help to figure out that.

add a .htaccess to the php directory with:

Order Deny,Allow
Deny from all