Get first day of week in PHP?

Question

Given a date MM-dd-yyyy format, can someone help me get the first day of the week?

Answer 1

This is what I am using to get the first and last day of the week from any date. In this case, monday is the first day of the week...

$date = date('Y-m-d') // you can put any date you want
$nbDay = date('N', strtotime($date));
$monday = new DateTime($date);
$sunday = new DateTime($date);
$monday->modify('-'.($nbDay-1).' days');
$sunday->modify('+'.(7-$nbDay).' days');

Answer 2

Here's a one liner for the first day of last week, and the last day of last week as a DateTime object.

$firstDay = (new \DateTime())->modify(sprintf('-%d day', date('w') + 7))
                             ->setTime(0, 0, 0);
$lastDay = (new \DateTime())->modify(sprintf('-%d day', date('w') + 1))
                            ->setTime(23, 59, 59);

Answer 3

A smart way of doing this is to let PHP handle timezone differences and Daylight Savings Time (DST). Let me show you how to do this.

This function will generate all days from Monday until Friday, inclusive (handy for generating work week days):

class DateTimeUtilities {
    public static function getPeriodFromMondayUntilFriday($offset = 'now') {
        $now = new \DateTimeImmutable($offset, new \DateTimeZone('UTC'));
        $today = $now->setTime(0, 0, 1);

        $daysFromMonday = $today->format('N') - 1;

        $monday = $today->sub(new \DateInterval(sprintf('P%dD', $daysFromMonday)));
        $saturday = $monday->add(new \DateInterval('P5D'));

        return new \DatePeriod($monday, new \DateInterval('P1D'), $saturday);
    }
}

foreach (DateTimeUtilities::getPeriodFromMondayUntilFriday() as $day) {
    print $day->format('c');
    print PHP_EOL;
}

This will return datetimes Monday-Friday for current week. To do the same for an arbitrary date, pass a date as a parameter to DateTimeUtilities ::getPeriodFromMondayUntilFriday, thus:

foreach (DateTimeUtilities::getPeriodFromMondayUntilFriday('2017-01-02T15:05:21+00:00') as $day) {
    print $day->format('c');
    print PHP_EOL;
}

//prints 
//2017-01-02T00:00:01+00:00
//2017-01-03T00:00:01+00:00
//2017-01-04T00:00:01+00:00
//2017-01-05T00:00:01+00:00
//2017-01-06T00:00:01+00:00

Only interested in Monday, as the OP asked?

$monday = DateTimeUtilities::getPeriodFromMondayUntilFriday('2017-01-02T15:05:21+00:00')->getStartDate()->format('c');
print $monday;
// prints
//2017-01-02T00:00:01+00:00

Answer 4

This question needs a good DateTime answer:-

function firstDayOfWeek($date)
{
    $day = DateTime::createFromFormat('m-d-Y', $date);
    $day->setISODate((int)$day->format('o'), (int)$day->format('W'), 1);
    return $day->format('m-d-Y');
}

var_dump(firstDayOfWeek('06-13-2013'));

Output:-

string '06-10-2013' (length=10)

This will deal with year boundaries and leap years.

Answer 5

$today_day = date('D'); //Or add your own date
$start_of_week = date('Ymd');
$end_of_week = date('Ymd');

if($today_day != "Mon")
    $start_of_week = date('Ymd', strtotime("last monday"));

if($today_day != "Sun")
                    $end_of_week = date('Ymd', strtotime("next sunday"));

Answer 6

For what it's worth, here is a breakdown of the wonky behavior of strtotime when determining a consistent frame of reference:

http://gamereplays.org/reference/strtotime.php

Basically only these strings will reliably give you the same date, no matter what day of the week you're currently on when you call them:

strtotime("next monday");
strtotime("this sunday");
strtotime("last sunday");