<?php
$date = new DateTime();
$ano=2018;
$semana=47;
echo $date->setISODate($ano, $semana)->format('d-m-Y');
echo PHP_EOL;
echo $date->setISODate($ano, $semana, 7)->format('d-m-Y');
PD9waHAKCiBkYXRlX2RlZmF1bHRfdGltZXpvbmVfc2V0KCdFdXJvcGUvQW1zdGVyZGFtJyk7CiAkZGF0ZSA9IG5ldyBEYXRlVGltZSgpOyAKCiAkYW5vPTIwMTg7CiAkc2VtYW5hPTQ3OwogCiBlY2hvICRkYXRlLT5zZXRJU09EYXRlKCRhbm8sICRzZW1hbmEpLT5mb3JtYXQoJ2QtbS1ZJyk7CgogZWNobyBQSFBfRU9MOwogICAgIAogZWNobyAkZGF0ZS0+c2V0SVNPRGF0ZSgkYW5vLCAkc2VtYW5hLCA3KS0+Zm9ybWF0KCdkLW0tWScpOyA=