What Can Use for Datetime::Diff() for PHP 5.2

How do I compare two DateTime objects in PHP 5.2.8?

The following seems to confirm that there are comparison operators for the DateTime class:

dev:~# php
<?php
date_default_timezone_set('Europe/London');

$d1 = new DateTime('2008-08-03 14:52:10');
$d2 = new DateTime('2008-01-03 11:11:10');
var_dump($d1 == $d2);
var_dump($d1 > $d2);
var_dump($d1 < $d2);
?>
bool(false)
bool(true)
bool(false)
dev:~# php -v
PHP 5.2.6-1+lenny3 with Suhosin-Patch 0.9.6.2 (cli) (built: Apr 26 2009 20:09:03)
Copyright (c) 1997-2008 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2008 Zend Technologies
dev:~#

How to use DateTime::diff() with DateTime::format('%R') in PHP 5.2?

Wouldn't it be enough to just check whether two dates are on the same day?

$start = new DateTime('13:00');
$end = new DateTime('02:00');

if ($start->format('Y-m-d') == $end->format('Y-m-d'))
 echo "Midnight has NOT passed";
else
 echo "Midnight has passed";

I can't see a scenario where this would not work because DST usually shifts the clocks at 2 in the morning (right?).

How to use DateTime::diff() with DateTime::format('%R') in PHP 5.2?

Wouldn't it be enough to just check whether two dates are on the same day?

$start = new DateTime('13:00');
$end = new DateTime('02:00');

if ($start->format('Y-m-d') == $end->format('Y-m-d'))
 echo "Midnight has NOT passed";
else
 echo "Midnight has passed";

I can't see a scenario where this would not work because DST usually shifts the clocks at 2 in the morning (right?).

Convert unix time to DateTime Object : PHP 5.2.X

Because PHP < 5.3 doesn't support the DateInterval class, DateTime::diff() (which is the right way to do this) is unavailable. You will need to do this manually for it to work in 5.2.x.

The math is actually quite simple:

// Get the difference between the two dates, in seconds
$diff = $future_date->format('U') - $now->format('U');

// Calculate the days component
$d = floor($diff / 86400);
$diff %= 86400;

// Calculate the hours component
$h = floor($diff / 3600);
$diff %= 3600;

// Calculate the minutes component
$m = floor($diff / 60);

// Calculate the seconds component
$s = $diff % 60;

// $d, $h, $m and $s now contain the values you want, so you can just build a
// string from them
$str = "$d d, $h h, $m m, $s s";

However with larger intervals this will introduce inaccuracies, because it does not take leap seconds into account. This means that you could end up a few seconds out - but since your original format string does not contain a seconds component, I doubt this will matter too much for what you are doing.

Note also that you need to subtract $now from $future_date, not the other way around, or the result will be negative.

See it working

How to calculate the difference between two dates using PHP?

Use this for legacy code (PHP < 5.3). For up to date solution see jurka's answer below

You can use strtotime() to convert two dates to unix time and then calculate the number of seconds between them. From this it's rather easy to calculate different time periods.

$date1 = "2007-03-24";
$date2 = "2009-06-26";

$diff = abs(strtotime($date2) - strtotime($date1));

$years = floor($diff / (365*60*60*24));
$months = floor(($diff - $years * 365*60*60*24) / (30*60*60*24));
$days = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24)/ (60*60*24));

printf("%d years, %d months, %d days\n", $years, $months, $days);

Edit: Obviously the preferred way of doing this is like described by jurka below. My code is generally only recommended if you don't have PHP 5.3 or better.

Several people in the comments have pointed out that the code above is only an approximation. I still believe that for most purposes that's fine, since the usage of a range is more to provide a sense of how much time has passed or remains rather than to provide precision - if you want to do that, just output the date.

Despite all that, I've decided to address the complaints. If you truly need an exact range but haven't got access to PHP 5.3, use the code below (it should work in PHP 4 as well). This is a direct port of the code that PHP uses internally to calculate ranges, with the exception that it doesn't take daylight savings time into account. That means that it's off by an hour at most, but except for that it should be correct.

<?php

/**
 * Calculate differences between two dates with precise semantics. Based on PHPs DateTime::diff()
 * implementation by Derick Rethans. Ported to PHP by Emil H, 2011-05-02. No rights reserved.
 * 
 * See here for original code:
 * http://svn.php.net/viewvc/php/php-src/trunk/ext/date/lib/tm2unixtime.c?revision=302890&view=markup
 * http://svn.php.net/viewvc/php/php-src/trunk/ext/date/lib/interval.c?revision=298973&view=markup
 */

function _date_range_limit($start, $end, $adj, $a, $b, $result)
{
    if ($result[$a] < $start) {
        $result[$b] -= intval(($start - $result[$a] - 1) / $adj) + 1;
        $result[$a] += $adj * intval(($start - $result[$a] - 1) / $adj + 1);
    }

    if ($result[$a] >= $end) {
        $result[$b] += intval($result[$a] / $adj);
        $result[$a] -= $adj * intval($result[$a] / $adj);
    }

    return $result;
}

function _date_range_limit_days($base, $result)
{
    $days_in_month_leap = array(31, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
    $days_in_month = array(31, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

    _date_range_limit(1, 13, 12, "m", "y", &$base);

    $year = $base["y"];
    $month = $base["m"];

    if (!$result["invert"]) {
        while ($result["d"] < 0) {
            $month--;
            if ($month < 1) {
                $month += 12;
                $year--;
            }

            $leapyear = $year % 400 == 0 || ($year % 100 != 0 && $year % 4 == 0);
            $days = $leapyear ? $days_in_month_leap[$month] : $days_in_month[$month];

            $result["d"] += $days;
            $result["m"]--;
        }
    } else {
        while ($result["d"] < 0) {
            $leapyear = $year % 400 == 0 || ($year % 100 != 0 && $year % 4 == 0);
            $days = $leapyear ? $days_in_month_leap[$month] : $days_in_month[$month];

            $result["d"] += $days;
            $result["m"]--;

            $month++;
            if ($month > 12) {
                $month -= 12;
                $year++;
            }
        }
    }

    return $result;
}

function _date_normalize($base, $result)
{
    $result = _date_range_limit(0, 60, 60, "s", "i", $result);
    $result = _date_range_limit(0, 60, 60, "i", "h", $result);
    $result = _date_range_limit(0, 24, 24, "h", "d", $result);
    $result = _date_range_limit(0, 12, 12, "m", "y", $result);

    $result = _date_range_limit_days(&$base, &$result);

    $result = _date_range_limit(0, 12, 12, "m", "y", $result);

    return $result;
}

/**
 * Accepts two unix timestamps.
 */
function _date_diff($one, $two)
{
    $invert = false;
    if ($one > $two) {
        list($one, $two) = array($two, $one);
        $invert = true;
    }

    $key = array("y", "m", "d", "h", "i", "s");
    $a = array_combine($key, array_map("intval", explode(" ", date("Y m d H i s", $one))));
    $b = array_combine($key, array_map("intval", explode(" ", date("Y m d H i s", $two))));

    $result = array();
    $result["y"] = $b["y"] - $a["y"];
    $result["m"] = $b["m"] - $a["m"];
    $result["d"] = $b["d"] - $a["d"];
    $result["h"] = $b["h"] - $a["h"];
    $result["i"] = $b["i"] - $a["i"];
    $result["s"] = $b["s"] - $a["s"];
    $result["invert"] = $invert ? 1 : 0;
    $result["days"] = intval(abs(($one - $two)/86400));

    if ($invert) {
        _date_normalize(&$a, &$result);
    } else {
        _date_normalize(&$b, &$result);
    }

    return $result;
}

$date = "1986-11-10 19:37:22";

print_r(_date_diff(strtotime($date), time()));
print_r(_date_diff(time(), strtotime($date)));

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