Hm, ich weiß, der Thread ist alt...
<?php
$data = shell_exec('uptime');
$uptime = explode(' up ', $data);
$uptime = explode(',', $uptime[1]);
$uptime = $uptime[0].', '.$uptime[1];
echo ('Current server uptime: '.$uptime.'
');
?>
Current server uptime: 6 days, 5:23...