$last_month = date(‘Y-m‘, strtotime(‘last month‘));
$last[‘first‘] = $last_month . ‘-01 00:00:00‘;
$last[‘end‘] = date(‘Y-m-d H:i:s’, strtotime("$last_month +1 month -1 day +23 hours +59 minutes +59 seconds"));
原文：http://www.cnblogs.com/gentsir/p/5857766.html