This is the simplest and most powerful file manager you can get to manage you server directories/files and even fully edit them (with a pretty nice code editor) using just your browser. Works fine with PHP 7.x and 8.x and nothing else.
This script allows copying/moving files/directories, compressing/extracting files/directories and even editing files online with code support to some languages like HTML, CSS and PHP.
To install this script on your server you just need to open the index.php file and set your desired values to the two variables at the top of the code. After that upload the index.php file to any directory in your server (no other file needs to be uploaded) and access it using your browser.