##When Date/Calendar recursion library for PHP 5.2+

by Thomas Planer, modified by James Paul Muir

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###About After a comprehensive search I couldn't find a PHP library which could handle recursive dates. There is: http://phpicalendar.org/ however it would have been extremely difficult to extract the recursion portion of the script from the application.

Oddly, there are extremely good date recursion libraries for both Ruby and Python:

Ruby: http://github.com/seejohnrun/ice_cube

Python: http://labix.org/python-dateutil

Since I couldn't find an equivalent for PHP I created When.

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###Unit Tests

Tests were written in PHPUnit (http://www.phpunit.de/)

Initial set of tests were created from the examples found within RFC5545 (http://tools.ietf.org/html/rfc5545).

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###Documentation

Initializing the class

$when = new When();

Once you have initialized the class you can create a recurring event by calling on the recur method

$when->recur(<DateTime object|valid Date string>, <yearly|monthly|weekly|daily>);

You can limit the number of dates to find by specifying a limit():

$when->limit(<int>);

Alternatively you can specify an end date:

$when->until(<DateTime object|valid Date String>);

Note: the end date does not have to match the recurring pattern.

Note: the script will stop returning results when either the limit or the end date is met.

More documentation to come, please take a look at the unit tests for an understanding of what the class is capable of.

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###Examples (take a look at the unit tests for more examples)

The next 5 occurrences of Friday the 13th:

$r = new When();
$r->recur(new DateTime(), 'monthly')
  ->count(5)
  ->byday(array('FR'))
  ->bymonthday(array(13));

while($result = $r->next())
{
	echo $result->format('c') . '<br />';
}

Every four years, the first Tuesday after a Monday in November, for the next 20 years (U.S. Presidential Election day):

// this is the next election date
$start = new DateTime('2012-09-06');

$r = new When();
$r->recur($start, 'yearly')
  ->until($start->modify('+20 years'))
  ->interval(4)
  ->bymonth(array(11))
  ->byday(array('TU'))
  ->bymonthday(array(2,3,4,5,6,7,8));

while($result = $r->next())
{
	echo $result->format('c') . '<br />';
}

You can now pass raw RRULE's to the class:

$r = new When();
$r->recur('19970922T090000')->rrule('FREQ=MONTHLY;COUNT=6;BYDAY=-2MO');

while($result = $r->next())
{
	echo $result->format('c') . '<br />';
}

Warnings:

• If you submit a pattern which has no results the script will loop infinitely.
• If you do not specify an end date (until) or a count for your pattern you must limit the number of results within your script to avoid an infinite loop.

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###Contributing

If you would like to contribute please create a fork and upon making changes submit a pull request.

Please ensure 100% pass of unit tests before submitting a pull request.

There are 78 tests, 1410 assertions currently.

>>>phpunit --verbose tests
PHPUnit 3.4.15 by Sebastian Bergmann.

tests
 When_Core_Tests
 ..

 When_Daily_Rrule_Test
 .....

 When_Daily_Test
 .....

 When_Iterator_Tests
 ..

 When_Monthly_Rrule_Test
 ..............

 When_Monthly_Test
 ..............

 When_Weekly_Rrule_Test
 ........

 When_Weekly_Test
 ........

 When_Rrule_Test
 ..........

 When_Yearly_Test
 ..........

Time: 2 seconds, Memory: 6.00Mb

OK (78 tests, 1410 assertions)

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###License

Copyright (c) 2010 Thomas Planer

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.