I want to get the date of the closest Monday in the future (i.e. not in the past).
So if today is Tuesday (Dec 1, 2009) I want to get the date of Monday (Dec 7, 2009).
How can I do this with Zend_Date
?
Let's say today is Tuesday and we wanted to get the upcoming Monday. Monday is 6 days into the future. So, we would add 6 days to get monday's date.
//like so:
$tuesday = Zend_Date::now();
$nextMonday = $tuesday->addDay(6);
To do this dynamically, we will need to determine which day of the week it is today:
$today = Zend_Date::now();
$dayNumber = $today->get(Zend_Date::WEEKDAY_DIGIT);
//dayNumber will now be equal to the numeric day of the week (0-6)
//example:
$weekdays = array(
0 => 'sunday',
1 => 'monday',
2 => 'tuesday' //etc...
);
To determine how many days we need to add to get the desired future day, we do the following:
$daysToAdd = ( $dayWanted - $todayDayNumber + 7 );
# $dayWanted = monday(1)
# $todayDayNumber = tuesday(2)
# 7 = number of days in a week (we don't want a negative number)
# 1 - 2 + 7 = 6 days into the future
$nextMonday = $today->addDay($daysToAdd);
Let's say the day we want is wednesday (tomorrow), one day into the future. Our previous solution won't work:
$daysToAdd = ( $dayWanted - $todayDayNumber + 7 );
# $dayWanted = wednesday(3)
# $todayDayNumber = tuesday(2)
# 7 = number of days in a week
# 3 - 2 + 7 = 8 days into the future (not 1)
We can solve this problem by adding the modulus operator (percent sign) to our formula to get the remainder of a division operation.
$daysToAdd = ( $dayWanted - $todayDayNumber + 7 ) % 7;
# (3 - 2 + 7) % 7
# $daysToAdd == 1 (remainder of 8 divided by 7)
$tomorrow = $today->addDay($daysToAdd);
Now our formula will work as expected...with the exception of one thing. If today is tuesday, and I want to get next tuesday, our formula will return today instead of a week from today:
$daysToAdd = ( $dayWanted - $todayDayNumber + 7 ) % 7;
# (2 - 2 + 7) % 7 == 0
# 7 goes into 7 evenly with no remainder
We will have to add a check to make sure it is not equal to zero.
if ($daysToAdd == 0) {
//give me the date a week from today, not today's date
$daysToAdd = 7;
}
public function outputDate()
{
$monday = $this->getDateOfNext('monday');
echo 'today: ' . Zend_Date::now()->toString(Zend_Date::RFC_850) . "<br>";
echo "monday: " . $monday->toString(Zend_Date::RFC_850);
}
private function getDateOfNext($dayWanted)
{
$weekdays = array('sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday');
if (!in_array($dayWanted, $weekdays)) {
throw new Exception("'$dayWanted' not found in array of possible weekdays");
}
$weekdays = array_flip($weekdays);
$date = Zend_Date::now();
$today = $date->get(Zend_Date::WEEKDAY_DIGIT);
$daysToAdd = ( $weekdays[$dayWanted] - $today + 7 ) % 7;
if ($daysToAdd == 0) {
//give me the date a week from today, not today's date
$daysToAdd = 7;
}
$date->addDay($daysToAdd);
return $date;
}
Here's the logic, laid out:
$days_per_week = 7;
$weekdays = array_flip(array('sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'));
$day_wanted = 'mon';
$days_forward =
( $weekdays[$day_wanted] - $date->get(Zend_Date::WEEKDAY_DIGIT) + $days_per_week )
% $days_per_week;
$date->addDay($days_forward);
That works nicely for any $day_wanted
.