ExpressiveDate::getDifferenceInSeconds PHP Method

    public function getDifferenceInSeconds($compare = null)
    {
        if (!$compare) {
            $compare = new ExpressiveDate(null, $this->getTimezone());
        }
        $difference = $this->diff($compare);
        list($days, $hours, $minutes, $seconds) = explode(':', $difference->format('%a:%h:%i:%s'));
        // Add the total amount of seconds in all the days.
        $seconds += $days * 24 * 60 * 60;
        // Add the total amount of seconds in all the hours.
        $seconds += $hours * 60 * 60;
        // Add the total amount of seconds in all the minutes.
        $seconds += $minutes * 60;
        return $seconds * $difference->format('%r1');
    }

function eme_client_clock_callback() {
   // Set php clock values in an array
   $phptime_obj = new ExpressiveDate(null,$eme_timezone);
   // if clock data not set
   if (!isset($_SESSION['eme_client_unixtime'])) {
      // Preset php clock values in client session variables for fall-back if valid client clock data isn't received.
      $_SESSION['eme_client_clock_valid'] = false; // Will be set true if all client clock data passes sanity tests
      $_SESSION['eme_client_php_difference'] = 0; // Client-php clock difference integer seconds
      $_SESSION['eme_client_unixtime'] = (int) $phptime_obj->format('U'); // Integer seconds since 1/1/1970 @ 12:00 AM
      $_SESSION['eme_client_seconds'] = (int) $phptime_obj->format('s'); // Integer second this minute (0-59)
      $_SESSION['eme_client_minutes'] = (int) $phptime_obj->format('i'); // Integer minute this hour (0-59)
      $_SESSION['eme_client_hours'] = (int) $phptime_obj->format('h'); // Integer hour this day (0-23)
      $_SESSION['eme_client_wday'] = (int) $phptime_obj->format('w'); // Integer day this week (0-6), 0 = Sunday, ... , 6 = Saturday
      $_SESSION['eme_client_mday'] = (int) $phptime_obj->format('j'); // Integer day this month 1-31)
      $_SESSION['eme_client_month'] = (int) $phptime_obj->format('n'); // Integer month this year (1-12)
      $_SESSION['eme_client_fullyear'] = (int) $phptime_obj->format('Y'); // Integer year (1970-9999)
      $ret = '1'; // reload from server
   } else {
      $ret = '0';
   }
   
   // Cast client clock values as integers to avoid mathematical errors and set in temporary local variables.
   $client_unixtime = (int) $_POST['client_unixtime'];
   $client_seconds = (int) $_POST['client_seconds'];
   $client_minutes = (int) $_POST['client_minutes'];
   $client_hours = (int) $_POST['client_hours'];
   $client_wday = (int) $_POST['client_wday'];
   $client_mday = (int) $_POST['client_mday'];
   $client_month = (int) $_POST['client_month'];
   $client_fullyear = (int) $_POST['client_fullyear'];
   
   // Client clock sanity tests
   $valid = true;
   if (abs($client_unixtime - $_SESSION['eme_client_unixtime']) > 300) $valid = false; // allow +/-5 min difference
   if (abs($client_seconds - 30) > 30) $valid = false; // Seconds <0 or >60
   if (abs($client_minutes - 30) > 30) $valid = false; // Minutes <0 or >60
   if (abs($client_hours - 12) > 12) $valid = false; // Hours <0 or >24
   if (abs($client_wday - 3) > 3) $valid = false; // Weekday <0 or >6
   if (abs($client_mday - $_SESSION['eme_client_mday']) > 30) $valid = false; // >30 day difference
   if (abs($client_month - $_SESSION['eme_client_month']) > 11) $valid = false; // >11 month difference
   if (abs($client_fullyear - $_SESSION['eme_client_fullyear']) > 1) $valid = false; // >1 year difference

   // To insure mutual consistency, don't use any client values unless they all passed the tests.
   if ($valid) {
      $_SESSION['eme_client_unixtime'] = $client_unixtime;
      $_SESSION['eme_client_seconds'] = $client_seconds;
      $_SESSION['eme_client_minutes'] = $client_minutes;
      $_SESSION['eme_client_hours'] = $client_hours;
      $_SESSION['eme_client_wday'] = $client_wday;
      $_SESSION['eme_client_mday'] = $client_mday;
      $_SESSION['eme_client_month'] = $client_month;
      $_SESSION['eme_client_fullyear'] = $client_fullyear;
      $_SESSION['eme_client_clock_valid'] = true;
      // Set  date & time clock strings
      $client_clock_str = "$client_fullyear-$client_month-$client_mday $client_hours:$client_minutes:$client_seconds";
      $client_clock_obj = new ExpressiveDate($client_clock_str,$eme_timezone);
      $_SESSION['eme_client_php_difference'] = (int) $client_clock_obj->getDifferenceInSeconds($phptime_obj);
   }
   
   // it is an ajax instance: echo the result
   echo $ret;
}