Get Week's Starting date

[catheirc]

From a given year and work week eg 46th week of year... i need to ouput the range of work week..

week 46 (Nov 20-26 )

please help!

thank you,
Cathei

RWC wrote:

Hi,

I think the only acceptable solution was given by Weedpacket.
All solutions which take the week number of January 1st as a base are definitely incorrect.

I have written a function which give back the correct date when you provide the day, the year and the week number. Maybe it can be of use to someone.

function datefromweeknr($aYear, $aWeek, $aDay)
{
$Days=array('xx','ma','di','wo','do','vr','za','zo');
$DayOfWeek=array_search($aDay,$Days); //get day of week (1=Monday)
$DayOfWeekRef = date("w", mktime (0,0,0,1,4,$aYear)); //get day of week of January 4 (always week 1)
if ($DayOfWeekRef==0)
$DayOfWeekRef=7;
$ResultDate=mktime(0,0,0,1,4,$aYear)+((($aWeek-1)7+($DayOfWeek-$DayOfWeekRef))86400);
return $ResultDate;
};

[catheirc]

how can we reverse the date('w') function of php? so i can output the daterange of the given workweek... is there calculation? please help....

[bretticus]

Well, I thought a simple google search and I would find an example to show you. Unfortunately, I did not find one (maybe somebody else is a better searcher.) Anyhow, I got thinking, this is something I'd like to put into my own bag of tricks for future projects. Thus, I hacked together the following function.

<?php
/**
 * Returns array of unix timestamps representing work week specified.
 *
 * @param integer $year
 * @param integer $weekOfYear
 * @param integer $daysToAdd
 * @return array
 */
function getWorkWeek($year,$weekOfYear, $daysToAdd=5)
{
	/*** Set number of seconds date constants ***/
	define("ONE_DAY", 60*60*24);
	define("ONE_WEEK", ONE_DAY * 7);
	/*** Initialize first day of specified year ***/
	$firstDayOfYear = mktime(0,0,0,1,1,$year);	
	/*** Add days to first day of year until we 
	 * finally end up with the first monday. ***/
	$firstMonday = $firstDayOfYear;
	while (date("w",$firstMonday) != 1) {	
		$firstMonday+=ONE_DAY;
	}
	/*** Get integer value of week of year first 
	 * monday falls in... ***/
	$firstWeekMondayIn = intval(date("W", $firstMonday));
	/*** Determine weeks to add ***/
	$weeksToAdd = $weekOfYear - $firstWeekMondayIn;
	/*** Add weeks to find first monday of week 
	 * of the year specified. ***/
	$startdate = $firstMonday + (ONE_WEEK * $weeksToAdd);
	/*** Add specified days to get end date ***/
	$enddate = $startdate + ($daysToAdd * ONE_DAY);
	/*** Build array of days in workweek range ***/
	$dates = array();
	for ($date=$startdate; $date<$enddate; $date+=ONE_DAY) {
		$dates[] = $date;
	}
	return $dates;
}
?>

Probably not tested thoroughly enough. Test it and let me know if it works for you.

[Installer]

This will get rid of those unsightly error notices (in the case of multiple function calls):

if (!defined('ONE_DAY')) {
    define("ONE_DAY", 60*60*24);
} 
if (!defined('ONE_WEEK')) {
    define("ONE_WEEK", ONE_DAY * 7);
}

BTW, Cathei, Nov 20-26 is the 47th week of 2006, not the 46th.

Edit: Here's a more concise way to do it:

function get_work_week($yr, $wk) 
{
    $day_ts = strtotime($yr . '-01-04');  // 01-04 is always in week #1
    while (date('w', $day_ts) != '1') { 
        $day_ts = strtotime('-1 day', $day_ts);
    }
    $day_ts = strtotime('+' . ($wk - 1) . ' weeks', $day_ts);
    for ($d = 0; $d < 7; $d++) {
        $dates_ts[$d] = strtotime('+' . $d . ' days', $day_ts);
    }
    return $dates_ts;
}

[bretticus]

You're an elegant coder Installer, thanks!