i should know this but don't

[Xenon]

it's a bit more complicated ^^

example from showthread.php:

PHP Code:

// set $perpage

if (!$perpage)
{
    $perpage = $bbuserinfo['maxposts'];
}

$checkmax = explode(',', $vboptions['usermaxposts'] . ',' . $vboptions['maxposts']);
if ($perpage < 1 OR $perpage > max($checkmax))
{
    $perpage = $vboptions['maxposts'];
} 


so $perpage can be defined in several ways, as parameter of the url, as a user setting, as $vboptions[mx] aso.