3v4l.org

run code in 300+ PHP versions simultaneously
<?php $lundi = strtotime('next monday'); $numWeekM6 = strftime('%U', strtotime('+3 week', $lundi) + 1); echo $lundi; echo ' - '; echo $numWeekM6;

preferences:
72.2 ms | 402 KiB | 5 Q