"listing directory /" page loaded via atom-live-server

On my localhost root folder, I have one file, index.php.

When starting the atom-live-server, it loads localhost:3000 (Firefox - Browser used), and then doesn't load my index.php page, but a "listing directory /" page, listing all the files inside the root folder (exclusively index.php). It's not displaying my index.php page.

(I've set index.php as the DirectoryIndex before index.html in the httpd.conf file of my localhost).

When I change the URL to localhost:80, my index.php file gets displayed properly. When however using the live server again, it switches back to the port 3000 address, back to the "listing directory /" page. What am I doing wrong?