1st我在PHP中将日期转换为星期数（01到53），现在我不知道如何将星期数转换为week的first_date

Question

Here a simple code of date to week_number of year and now. How can I get start_date and end_date of week_number

$date_string = "2012-12-30";
echo "Weeknummer: " . date("W", strtotime($date_string));

Answer 1

You can use this:

<?php
    $date_string = "2012-12-30";
    $weekNumber = date("W", strtotime($date_string));

    echo "Weeknummer: ".$weekNumber;
    echo '</br>';
    // get the year
    $year = date("Y", strtotime($date_string));
    // set the date string for the week number
    $dateWeek = $year.'-W'.$weekNumber;

    // increase the weekNumber to the next
    $weekNumber = intval($weekNumber);
    $weekNumber += 1;

    // if it is lower than 10 add preceeding 0
    if($weekNumber < 10) $weekNumber = '0'.$weekNumber;

    // set the date string for the next week number
    $dateWeekNext = $year.'-W'.$weekNumber;

    echo '</br>';
    // get the first day of the week
    echo date('Y-m-d', strtotime($dateWeek));
    echo '</br>';
    // get the day before the first day of the next week
    echo date('Y-m-d', strtotime($dateWeekNext . ' -1 day'));
?>

This outputs:

Weeknummer: 52

2012-12-24
2012-12-30

Answer 2

There is many ways to do it, here is one.
I use "N" of date to determine what day the selected day is and use strtotimes way of understanding simple text to find previous or next Monday/Sunday.

$date_string = "2018-01-27";
$w =date("W", strtotime($date_string));
$N =date("N", strtotime($date_string));
If($N == 1){ // if monday
    $monday = $date_string;
    $sunday = date("Y-m-d", strtotime("next Sunday $date_string"));
}Elseif($N ==7){ // if sunday
    $monday = date("Y-m-d", strtotime("previous Monday $date_string"));
    $sunday = $date_string;
}Else{// any other weekday
    $monday = date("Y-m-d", strtotime("previous Monday $date_string"));
    $sunday = date("Y-m-d", strtotime("next Sunday $date_string"));
}


echo "Weeknummer: $w.\nMonday: $monday.\nSunday: $sunday.";

Output:

Weeknummer: 52.
Monday: 2012-12-24.
Sunday: 2012-12-30.

https://3v4l.org/UDoqF