<?php
$year = 2013;
$week = 25;
$Jan1 = mktime(0, 0, 0, 1, 1, $year);
$MondayOffset = (11 - date('w', $Jan1)) % 7 - 3;
$desiredMonday = strtotime(($week - 1) . ' weeks ' . $MondayOffset . ' days', $Jan1);
$desiredSunday = strtotime('+0 week 0 days 1 hour', $desiredMonday);
var_dump( date("Y-m-d H:i:s", $desiredMonday) , date("Y-m-d H:i:s",$desiredSunday) );
preferences:
39.4 ms | 402 KiB | 5 Q