3v4l.org

run code in 500+ PHP versions simultaneously
<?php $yr="2011"; $week="01"; $day="Monday"; $day=date("D",strtotime($day)); echo date("Y-m-d", strtotime($yr."W".$week."D ".$day));; ?>
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9
1970-01-01
Output for 5.0.0 - 5.0.5
2010-12-19
Output for 5.1.0 - 5.1.6
2011-01-02
Output for 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.34, 8.3.0 - 8.3.35, 8.4.1 - 8.4.26, 8.5.0 - 8.5.11
2011-01-04
preferences:
34.22 ms | 1163 KiB | 13 Q