Options +FollowSymlinks
RewriteEngine on
# This will rewrite http://mysite/campaignslug to http://mysite/index.php?campaign=campaignslug
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/]+)$ index.php?campaign=$1 [L]
# This will rewrite http://mysite/campaignslug/galleryslug to http://mysite/index.php?campaign=campaignslug&gallery=galleryslug
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/]+)/([^/]+)$ index.php?campaign=$1&gallery=$2 [L]