Online PHP editor | refs for E5Neh

<?php $array = array ( 'AZ' => array ( 1 => '2020-01', 2 => '2020-02' ), 'BY' => array ( 0 => '2020-03', 1 => '2020-04' ), 'CX' => array ( 1 => '2020-05', 2 => '2020-06', 3 => '2020-07' ), 'DW' => array ( 106 => '2019-01', 107 => '2019-02', 108 => '2019-03' ) ); array_walk_recursive($array, function (&$v) { $v = preg_replace('/^(\d{4})-\d\d$/', '$1', $v); }); print_r($array);