Get date difference in PHP

 Following code is used for date difference 

<?php 

date_default_timezone_set("Asia/Calcutta");

//Set your time zone

/* this is the function for date difference */ 

function dt_differ($start, $end){
  $start = date("G:i:s:m:d:Y", strtotime($start));
  $date1=explode(":", $start);

  $end  = date("G:i:s:m:d:Y", strtotime($end));
  $date2=explode(":", $end);
 
  $starttime = mktime(date($date1[0]),date($date1[1]),

date($date1[2]),
  date($date1[3]),date($date1[4]),date($date1[5]));
  $endtime   = mktime(date($date2[0]),date($date2[1]),

date($date2[2]),
  date($date2[3]),date($date2[4]),date($date2[5]));

  $seconds_dif = $starttime-$endtime;

  return $seconds_dif;
} 

/* end of function */

  $today = date("Y-n-j H:i:s");
  $fromday = "2012-12-31 23:59:59";
  $timediffer = dt_differ($fromday, $today); 

//call date difference function
  echo $timediffer." seconds";