Recurring Events

PHP
1

Hi guys, I’m in search of a function that can calculate from a given date when an event would recur and then possibly return everything in an array. I’ve been trying to do this all day with no luck. Below is what I kind of already have.

	
function get_events($origDate, $startDate, $endDate, $recurIntval)
{
	$events = array();
	
	$dateDiff = $origDate - $startDate;
	
	// Needs to be more calculations here
	
	while ($recurDate >= $startDate && $recurDate <= $endDate)
	{
		$events[] = array('date' => $recurDate);
	
		$recurDate += $recurIntval;
	}
	
	return $events;
}

Assuming that all the parameters are in seconds. If anyone could help me out, I’ll greatly appreciate it.

2

Can you give an example?

3

Well let’s say for example, 25th of December is Christmas (which is 1293235200 seconds for this year), we know that that comes every year same date so if I add on 31536000 seconds (1 year) to that, I’ll get 2011’s Christmas. But I also want to constrain the events returned based on startDate and endDate (because it’s for a calendar).

<?php
	$origDate = 1293235200; // 25th of December;
	$recurIntval = 31536000; // 1 year
	$startDate = 1291161600; // 1st of December
	$endDate = 1293753600; // 31st of December
?>
4

Sorry, not sure what you actually want to achieve, but adding 31536000 won’t work due to leap years, try strtotime(‘+1 year’, $time)

5

Hmm, that’s what I was originally doing but I thought I might be able to save time by just doing calculation when it’s added the database. Good to know, thanks.

6

You’ll have trouble on a leap year.

How about using strtotime ?


$year = 2011;
$origDate = strottime('25 december ' . $year);
$reoccur = '+1 year';
$nextYear = strtotime($reoccur, $origDate);
7

I finally got the sucker to work! Thanks for the info about strtotime, that’s what I really needed all along.

For anyone interested,

<?php
$type = array('day', 'week', 'month', 'year');
		
$date = strtotime($event['date']);
$interval = $type[$event['interval']];
$frequency = $event['frequency'];
$diff = $start - $date;

if ($diff > 0)
{	
	$days = floor($diff/86400);
	$startDate = strtotime("+$days day", $date);
}
else
{
	$start = $date;
}
			
for ($repeat = $start; $repeat <= $end; $repeat = strtotime("+$frequency $interval", $repeat))
{
	$events[] = array(
		'date' => $repeat,
	);
}
?>

$event is array from the database. $start and $end are in seconds, and is the range.

EDIT: Spoke too soon, the range isn’t working.
EDIT2: Okay now it’s working, converting seconds to days and then rounding that value seems to have fixed it.

8

If you have PHP 5.3 available, this is as simple as:


$date = new DateTime($event);
$recurrance = $date->modify($interval);

Don’t know if that’s an option, but it’s a heck of a lot simpler than the awful strtotime functions.

Check out http://us2.php.net/manual/en/class.datetime.php for details.

9

You can actually use DateTime + DateInterval + DatePeriod.

Something I just noticed, is the DateTime constructor can’t take a unix timestamp, and they don’t provide a factory for it either. That’s pretty lame…all you get is $dt->setTimestamp()

10

I ran into the same thing earlier this week. The DT class actually provides a couple of different methods for time comparison (add, modify and sub) and is nice because you can do simple comparisons between different objects natively ($datetime1 >= $datetime2, etc). It’s a solid class, but the fact that there’s only a String constructor bugs me.

11

I guess that they’re making plans to do away with the 32-bit timestamp, in prepreation for dealing with the 2038 date problem.