Online PHP editor | refs for ilCIj

<?php $array = [ 'field_5abcb693a68bc' => [ 0 => [ 'field_5abcbb1b51ddf' => 'mortgage', 'field_5ae58a0b58b58' => '', 'field_5abcbb1e51de0' => '10', 'field_5abcbb2051de1' => 'הידגלה', 'field_5abcbb2351de2' => '45,654,456', 'field_5abcbb6251de3' => '', 'field_5abcbb6651de4' => '04/2017', 'field_5abcbb6851de5' => '4,454,656', 'field_5abcbb6b51de6' => '24/07/2018', 'field_5abcbbb351de7' => '657', 'field_5abcbbb651de8' => '24/07/2018', 'field_5abcbbb851de9' => '15', 'field_5abcbbbb51dea' => 'yes' ] ] ]; foreach ($array as &$set) { foreach ($set as &$subset) { $subset = preg_replace('~^\d[1-9]/[1-9]\d{3}$~', '01/$0', $subset); } } unset($set, $subset); // avoid future variable interferences var_export($array);