How to get the first day of a given week number in PHP (multi-platform)?

What is the simplest way to do it in PHP ?

I want the date of the Monday of a given week number of a year (example : week number 3 of 2009)

Thanks !

EDIT : If you use Linux only machines, use cletus' solution开发者_如何学Python, however I am looking for something that can work on Windows AND Linux.

It's simple on PHP 5.3

echo date('M d',strtotime('2013W15'));

where 15 is the number of week. But for the number below ten make sure it is in the format of 01, 02 for first week and second week.

Yet another solution:

<?php
        $week = 3;
        $year = 2009;

        $timestamp = mktime( 0, 0, 0, 1, 1,  $year ) + ( $week * 7 * 24 * 60 * 60 );
        $timestamp_for_monday = $timestamp - 86400 * ( date( 'N', $timestamp ) - 1 );
        $date_for_monday = date( 'Y-m-d', $timestamp_for_monday );
?>

A nice way to get this in a clean way is by using php DateTime class.

$year = 2015;
$week_no = 1;

$date = new DateTime();
$date->setISODate($year,$week_no);
echo $date->format('d-M-Y'); 

This would result into : 29-12-2014

You can use strptime() to get the time.

$time = strptime('1 23 2009', '%w %U %Y');

This will get the time for the Monday (day 1, 0 is Sunday, 6 is Saturday) of the 23rd week of 2009. If you want to format this into a date, use date().

$date = date('d F Y', $time);

This next script gives the 7 days of an specific week of a year

$time = new DateTime();
$time->setISODate(2016, 13);
for($i=0;$i<7;$i++){
    echo $time->format('d-M-Y') . '<br />';
    $time->add(new DateInterval('P1D'));
}

Seems to be working and not dependent of the server OS :

<?php

  $week = 4;
  $year = 2013;

  $timestamp_for_monday = mktime( 0, 0, 0, 1, 1,  $year ) + ((7+1-(date( 'N', mktime( 0, 0, 0, 1, 1,  $year ) )))*86400) + ($week-2)*7*86400 + 1 ;

?>

the idea is to add :

• the timestamp of the first of January of the chosen year
• the number of seconds to reach the end of the first week (which is 7 days minus the day of week of the 1st of January + 1 day) multiplied by the number of seconds per day
• the number of seconds of the number of chosen weeks minus the first week and the current week
• 1 second to reach the fist second of the current week

My example returns : 1358722801 which is the timestamp of 2013/01/21 0:00:01

Here is very simple solution, passing a week no and returns the date.

The ISO8601 standard states that week 1 always fall on the week where Jan 4 falls.

For example, to get a day in the 4th week of the year:

$day_in_week = strtotime("2006-01-04 + 4 weeks"));

Then you can adjust this value to Sunday (as a starting place you can guarantee that you can find):

// Find that day's day of the week (value of 0-6)
$wday = date('w', $day_in_week);
$offset = 6 - $wday; // How far it is from Sunday.
$sunday_in_week = $day_in_week - ($offset * (60 * 60 * 24)); // $offset * seconds in a day

Then, you add the seconds in a day again to get Monday.

$monday_in_week = $sunday_in_week + (60 * 60 * 24);

Note: This method can occasionally have some problems with daylight savings time. A similar, and slightly safer between DST time changes, method would use the DateTime class. However, DateTime is only support in PHP 5.2.0 or later. The method above works in earlier version as well.

Try this function

function MondayOfWeek($WeekNumber, $Year=-1) {
    if ($Year == -1) $Year   = 0+date("Y");
    $NewYearDate             = mktime(0,0,0,1,1,$Year);
    $FirstMondayDate         = 7 + 1 - date("w", mktime(0,0,0,1,1,2009));
    $Dates_fromFirstMonday   = 7 * $WeekNumber;
    $Second_fromFirstMonday  = 60*60*24*($FirstMondayDate + $Dates_fromFirstMonday);
    $MondayDay_ofWeek        = $NewYearDate + $Second_fromFirstMonday;
    $Date_ofMondayDay_ofWeek = 0+date("j", $MondayDay_ofWeek);
    return $Date_ofMondayDay_ofWeek;
}

for($i = 0; $i 

-5-12-19-26-2-9-16-23-2-9-16-23-30-6-13-20-27-4-11-18-25-1-8-15-22-29-6-13-20-27-3-10-17-24-31-7-14-21-28-5-12-19-26-2-9-16-23-30-7-14-21-28

Hope this helps.

I required same in the java script..so i converted.

function(week,year){
var timestamp = new Date(year, 0, 1, 0, 0, 0, 0);
var dateObj=new Date();
var val = timestamp.getTime(); 
days=( week * 7 * 24 * 60 * 60*1000 );
val=val+days;
var timestamp_for_monday =val - 86400 *((timestamp.getDay()-1000));
var weekdate=new Date(timestamp_for_monday);
return weekdate;
}