3v4l.org

run code in 300+ PHP versions simultaneously
<?php $format = 'Y-m-d'; $reqDate = date ( $format, strtotime ( '2014-03-30' ) )."\n"; echo $reqDate; // - 1 month echo date ( $format, strtotime ( $reqDate.' -1 month' ) );

preferences:
47.79 ms | 402 KiB | 5 Q