PHP: UNIX Date Difference calculations

datediff.php

<?php
  /**
   * Date Difference calculations for UNIX time stamps and Dates
   */
  // Set timezone
  date_default_timezone_set("UTC");
 
  // Time format is UNIX timestamp or
  // PHP strtotime compatible strings
  function dateDiff($time1, $time2, $precision = 6) {
    // If not numeric then convert texts to unix timestamps
    if (!is_int($time1)) {
      $time1 = strtotime($time1);
    }
    if (!is_int($time2)) {
      $time2 = strtotime($time2);
    }
 
    // If time1 is bigger than time2
    // Then swap time1 and time2
    if ($time1 > $time2) {
      $ttime = $time1;
      $time1 = $time2;
      $time2 = $ttime;
    }
 
    // Set up intervals and diffs arrays
    $intervals = array('year','month','day','hour','minute','second');
    $diffs = array();
 
    // Loop thru all intervals
    foreach ($intervals as $interval) {
      // Set default diff to 0
      $diffs[$interval] = 0;
      // Create temp time from time1 and interval
      $ttime = strtotime("+1 " . $interval, $time1);
      // Loop until temp time is smaller than time2
      while ($time2 >= $ttime) {
	$time1 = $ttime;
	$diffs[$interval]++;
	// Create new temp time from time1 and interval
	$ttime = strtotime("+1 " . $interval, $time1);
      }
    }
 
    $count = 0;
    $times = array();
    // Loop thru all diffs
    foreach ($diffs as $interval => $value) {
      // Break if we have needed precission
      if ($count >= $precision) {
	break;
      }
      // Add value and interval 
      // if value is bigger than 0
      if ($value > 0) {
	// Add s if value is not 1
	if ($value != 1) {
	  $interval .= "s";
	}
	// Add value and interval to times array
	$times[] = $value . " " . $interval;
	$count++;
      }
    }
 
    // Return string with times
    return implode(", ", $times);
  }
 
?>


<?php // USAGE #1 strtotime examples
echo dateDiff("2010-01-26", "2004-01-26") . "\n";
echo dateDiff("2006-04-12 12:30:00", "1987-04-12 12:30:01") . "\n";
echo dateDiff("now", "now +2 months") . "\n";
echo dateDiff("now", "now -6 year -2 months -10 days") . "\n";
echo dateDiff("2009-01-26", "2004-01-26 15:38:11") . "\n";
?>
<?php // Unix timestamp + precision
echo dateDiff(time(), time()-1000000, 1) . "\n";
echo dateDiff(time(), time()-1000000, 3) . "\n";
echo dateDiff(time(), time()-1000000, 6) . "\n";
?>
<?php // Converting text format back to UNIX timestamp example
$time1 = time();
$time2 = $time1-10000000;
echo $diff = dateDiff($time1, $time2) . "\n";
echo $time1 . "\n";
echo strtotime(" +".$diff, $time2) . "\n";
?>