Online PHP editor | refs for LSQRg

<?php $array = array( "date_2019_12" => 0, "date_2019_11" => 0, "date_2019_10" => 0, "date_2019_09" => 0, "date_2019_08" => 0, "date_2019_07" => 0, "date_2019_06" => 0, "date_2019_05" => 0, "date_2019_04" => 0, "date_2019_03" => 0, "date_2019_02" => 0, "date_2019_01" => 10, "date_2018_12" => 1, "date_2018_11" => 2, "date_2018_10" => 3, "date_2018_09" => 4, "date_2018_08" => 5, "date_2018_07" => 6, ); krsort($array); $year = "2019"; $keys = array_keys($array); foreach(array_values($array) as $k => $v){ if(strpos($keys[$k], $year) !== false) $res[$keys[$k]] = array_sum(array_slice($array, $k, 6)); } var_dump($res);