- explode: documentation ( source)
- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$yr="2014";
$week="01";
$day="02";
$day=date("D",strtotime($day));
$newdate= date("d-m-Y", strtotime($yr."W".$week."D ".$day));;
echo $newdate;
$k = explode("-", $newdate);
$ymd = $k[2]."-".$k[0]."-".$k[1];
echo $ymd
?>