$day=date("Y-m-d",time());
$day ="28-03-2015";
$day =date("Y-M-d",strtotime($day));
var_dump(time());
var_dump($day);
$day2 = date("Y-m",strtotime($day));
$day3 = strtotime($day2);
var_dump($day3);
var_dump("Y-m-d",$day3);
var_dump(date("Y-m-01 00:00:00",$day3));
var_dump(strtotime(date("Y-m-01 00:00:00",time()))); 月初時間。
var_dump($day2);
var_dump(mktime(23, 59, 59, date('m', strtotime($day))+1, 00));

var_dump(date("Y-m-d H-i-s",mktime(23, 59, 59, date('m', strtotime($day))+1, 00)));exit;//月末時間