in smf, everything is driven / processed by index.php. files with this name is also used as the default startup page when a website / directory is accessed.

if you don’t want to use the forum as the default page and want to write your own, one way is to install the forum in a subdirectory. but if you want to use the same directory as the forum, you can rename the file and write your own index.php.

to rename index.php to [newname].php:

• vi Sources/QueryString.php
• search for $scripturl = $boardurl . ‘/index.php’; - replace index.php with [newname].php

this information is taken from one of smf’s forum post [link…]