如何在一周和几年之间找到一周的差异

Question

I have a set of weeks and years like

$wk_det1 = array(36,2013);//ISO week assuming 52 weeks in a year, Year the said week belongs to
$wk_det2 = array(51,2012);

I need to find difference in weeks between $wk_det1 and $wk_det2. This might be simple but I can't quite figure it out. Any ideas how to do this?

PS: this is for php4, just in case

Answer 1

Each year has 52 weeks, so 2013 years is 2013*52 weeks, and 2011 years is 2011*52 weeks; the difference between the two (given that they are in the same week) is 52*(2013-2011) weeks.

The difference can be expressed simply as 52*($wk_det2[1]-$wek_det1[1])+$wk_det2[0]-$wk_det1[0];.

The logic works like this:

define("WEEKS_PER_YEAR", 52);

$week1_yr = $wk_det1[1];
$week2_yr = $wk_det2[1];
$yr_diff = $week2_yr - $week1_yr;

$week1_wk = $wk_det1[0];
$week2_wk = $wk_det2[0];
$wk_diff = $week2_wk - $week1_wk;

$total_wk_diff = WEEKS_PER_YEAR*$yr_diff+$wk_diff;