php 计算时间差

$season = ceil((date('n'))/3);//当月是第几季度
echo $season;
/* 
echo '<br>本季度:<br>';
echo date('Y-m-d H:i:s', mktime(0, 0, 0,$season*3-3+1,1,date('Y'))),"\n";
echo date('Y-m-d H:i:s', mktime(23,59,59,$season*3,date('t',mktime(0, 0 , 0,$season*3,1,date("Y"))),date('Y'))),"\n"; */
$a = date('Y-m-d H:i:s', mktime(0, 0, 0,$season*3-3+1,1,date('Y')));
$b = date('Y-m-d H:i:s', mktime(23,59,59,$season*3,date('t',mktime(0, 0 , 0,$season*3,1,date("Y"))),date('Y')));


$begin = strtotime($a);
$end = strtotime($b);
$res = timediff($begin,$end);
print_r($res);
function timediff( $begin_time, $end_time )
{
  if ( $begin_time < $end_time ) {
    $starttime = $begin_time;
    $endtime = $end_time;
  } else {
    $starttime = $end_time;
    $endtime = $begin_time;
  }
  $timediff = $endtime - $starttime;
  $days = intval( $timediff / 86400 );
  $remain = $timediff % 86400;
  $hours = intval( $remain / 3600 );
  $remain = $remain % 3600;
  $mins = intval( $remain / 60 );
  $secs = $remain % 60;
  $res = array( "day" => $days, "hour" => $hours, "min" => $mins, "sec" => $secs );
  return $res;
}