Get a date diff between 2 dates

dateDiff.php

/*
example:
$count_from = "2010-09-30 00:00:01"; // 24-Hour Format: YYYY-MM-DD HH:MM:SS"
$count_to = date("Y-m-d H:i:s");//today (2012-08-23 00:00:01)
echo datediff("d",$count_from,$count_to);
return: 693 (days)
*/

function datediff($interval, $datefrom, $dateto, $using_timestamps = false) {
  /*
    $interval can be:
    yyyy - Number of full years
    q - Number of full quarters
    m - Number of full months
    y - Difference between day numbers
      (eg 1st Jan 2004 is "1", the first day. 2nd Feb 2003 is "33". The datediff is "-32".)
    d - Number of full days
    w - Number of full weekdays
    ww - Number of full weeks
    h - Number of full hours
    n - Number of full minutes
    s - Number of full seconds (default)
  */
  
  if (!$using_timestamps) {
    $datefrom = strtotime($datefrom, 0);
    $dateto = strtotime($dateto, 0);
  }
  $difference = $dateto - $datefrom; // Difference in seconds
   
  switch($interval) {
   
    case 'yyyy': // Number of full years

      $years_difference = floor($difference / 31536000);
      if (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom), date("j", $datefrom), date("Y", $datefrom)+$years_difference) > $dateto) {
        $years_difference--;
      }
      if (mktime(date("H", $dateto), date("i", $dateto), date("s", $dateto), date("n", $dateto), date("j", $dateto), date("Y", $dateto)-($years_difference+1)) > $datefrom) {
        $years_difference++;
      }
      $datediff = $years_difference;
      break;

    case "q": // Number of full quarters

      $quarters_difference = floor($difference / 8035200);
      while (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom)+($quarters_difference*3), date("j", $dateto), date("Y", $datefrom)) < $dateto) {
        $months_difference++;
      }
      $quarters_difference--;
      $datediff = $quarters_difference;
      break;

    case "m": // Number of full months

      $months_difference = floor($difference / 2678400);
      while (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom)+($months_difference), date("j", $dateto), date("Y", $datefrom)) < $dateto) {
        $months_difference++;
      }
      $months_difference--;
      $datediff = $months_difference;
      break;

    case 'y': // Difference between day numbers

      $datediff = date("z", $dateto) - date("z", $datefrom);
      break;

    case "d": // Number of full days

      $datediff = floor($difference / 86400);
      break;

    case "w": // Number of full weekdays

      $days_difference = floor($difference / 86400);
      $weeks_difference = floor($days_difference / 7); // Complete weeks
      $first_day = date("w", $datefrom);
      $days_remainder = floor($days_difference % 7);
      $odd_days = $first_day + $days_remainder; // Do we have a Saturday or Sunday in the remainder?
      if ($odd_days > 7) { // Sunday
        $days_remainder--;
      }
      if ($odd_days > 6) { // Saturday
        $days_remainder--;
      }
      $datediff = ($weeks_difference * 5) + $days_remainder;
      break;

    case "ww": // Number of full weeks

      $datediff = floor($difference / 604800);
      break;

    case "h": // Number of full hours

      $datediff = floor($difference / 3600);
      break;

    case "n": // Number of full minutes

      $datediff = floor($difference / 60);
      break;

    default: // Number of full seconds (default)

      $datediff = $difference;
      break;
  }    

  return $datediff;
}