Relative time function

[wyattstorch42]

<?php
  /***************************************************
   * rel_time(mixed $from[, mixed $to = null])       *
   * Generates a string listing time units between   *
   * two specified times.                            *
   *                                                 *
   * @param mixed $from Integer generated from       *
   *  time() or a string that can be converted to a  *
   *  time integer via strtotime()                   *
   * @param mixed $to Integer generated from time()  *
   *  or a string that can be converted to a time    *
   *  integer via strtotime(), or null (evaluates as *
   *  time())                                        *
   *                                                 *
   * Returns a string with a format like so:         *
   *  "1 week, 2 days, 3 hours, 4 minutes, and 5     *
   *  seconds ago"                                   *
   ***************************************************/

  function rel_time($from, $to = null)
  {
   $to = $to === null ? time() : $to;
   $to = is_int($to) ? $to : strtotime($to);
   $from = is_int($from) ? $from : strtotime($from);

   $units = array
   (
    "year"   => 29030400, // seconds in a year   (12 months)
    "month"  => 2419200,  // seconds in a month  (4 weeks)
    "week"   => 604800,   // seconds in a week   (7 days)
    "day"    => 86400,    // seconds in a day    (24 hours)
    "hour"   => 3600,     // seconds in an hour  (60 minutes)
    "minute" => 60,       // seconds in a minute (60 seconds)
    "second" => 1         // 1 second
   );

   $diff = abs($from - $to);
   $suffix = $from > $to ? "from now" : "ago";

   foreach($units as $unit => $mult)
    if($diff >= $mult)
    {
     $and = $mult != 1 ? "" : "and ";
     $output .= ", ".$and.intval($diff / $mult)." ".$unit.(intval($diff / $mult) == 1 ? "" : "s");
     $diff -= intval($diff / $mult) * $mult;
    }
   $output .= " ".$suffix;
   $output = substr($output, strlen(", "));

   return $output;
  }
?>

<p>Test for <strong>September 2, 2010 4:20 PM</strong>:</p>
<p><?php echo rel_time("September 2, 2010 4:20 PM"); ?></p>

Critique?

Thank you.
--"Ellis Wyatt"

[bradgrafelman]

My only critique is that not every day is 86400 seconds in length (same for week, month, and year).

[wyattstorch42]

bradgrafelman;10970584 wrote:

My only critique is that not every day is 86400 seconds in length (same for week, month, and year).

Days vary in length? I know you're right in terms of a month (and so, obviously, a year), but I would think that every day is precisely 24 hours long in terms of a clock.

Pulling out my calculator, 2629800 would better represent the number of seconds in a month (average number of days in a month * 24 hours). I should probably remove weeks from the system altogether. Then 31557600 represents a year.

And there's probably an alternative by manually selecting portions of a date given from the time integer and determining how many months, days, minutes, seconds, etc. are different, but that seems more complicated.

Anyway, thank you for your critique. Much appreciated.

[bradgrafelman]

wyattstorch42 wrote:

Days vary in length?

Aye; depending upon which country/timezone you're in, some days are +/- 1 hour off of 24 hours.

[madrazel]

Not to mention leap seconds: http://en.wikipedia.org/wiki/Leap_second

[Weedpacket]

You fail to initialise $output [noparse]🙂[/noparse].

Whether it's accurate or not ... well, one criterion would be that if as of now a certain date was "4 months, 2 weeks, 2 days, 10 hours, 38 minutes, and 42 seconds ago" (personally I'd prefer the result to not be formatted so that I could do that myself without having to tinker with the function...) then you would expect that adding 4 months, 2 weeks, 2 days, 10 hours, 31 minutes, and 27 seconds to the date in question would bring you back to now.

$then = strtotime('September 2, 2010 4:20 PM');
$now = strtotime('4 months', $then);
$now = strtotime('2 weeks', $now);
$now = strtotime('2 days', $now);
$now = strtotime('10 hours', $now);
$now = strtotime('38 minutes', $now);
$now = strtotime('42 seconds', $now);

My testing gives a result that's off by ten days (less an hour, which would have been caused by crossing a daylight saving boundary).