Hacked every mention of "/portal.php?what=link&item=unixtimestamp"
into
/linkportal/unixtimestamp.php

Then created a new folder called linkportal and then created a .htaccess document in this new folder. the Mod_Rewrite rules in this doc are:

RewriteBase /linkportal/
RewriteEngine on
RewriteRule ^(.*).php$ /portal.php?what=link&item=$1 [NC,L]