加在第39行代码以前就行：

$Letter = $core->load_module('letter');
$today  = $Letter->get_total(array('begin_time'=>'today'));
$all  = $Letter->get_total();
$Y = date('Y');
$filter_2015['department'] = '';
$filter_2015['begin_time'] = $Y.'-01-01 00:00:00';
$filter_2015['end_time'] = '';
$total_this_year = $Letter->get_total($filter_2015);