VBScript's "DateDiff" function is very useful, allowing you to quickly determine time intervals between customer dates. PHP, unfortunately, had no function to perform the same task. Instead, you must rely on a combination of the date() function and it's power and timestamps - not always the most effective way to handle dates and times.
With this in mind, the PHP DateDiff function below is intended to allow you to very quickly make the most of the power of PHP, and give you quick access to time interval functions. It is based upon the VBScript function of the same name, with a couple of small changes.
To use the below, call it like a normal function. There are four arguments. The first determines what you want to measure the date difference in - years, months, quarters, etc - and the allowed values of this are listed in the first few lines of the function. The next two are the dates themselves. Any valid date should work just fine. You can also use timestamps as dates, although if you do, you must set the last of the four arguments to "true". You can call it like so:
echo datediff('w', '9 July 2003', '4 March 2004', false);Which will tell you the number of weekdays between the 9th July 2003 and the 4th of March 2004.
<?php
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 $datediff;
}
?>
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$datediff = floor($difference / 86400);
Very buggy implementation, since day IS NOT a 24 hours (can be also 23 and 25 due to daylight savings).
Using this function can cause +-1 day error.
PEAR::DATE and ADODB::TIME libs have, instead, correct handling of days differences