- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$yr="2014";
$dif=2012-$yr;if($dif != 0) $dif=$dif+1;
$week="01";
$day="Monday";
$day=date("D",strtotime($day));
echo date("Y-m-d", strtotime($yr."W".$week."D ".$day)-(86000*$dif));;
echo $dif;
?>