Online PHP editor | refs for aGU5D

<?php $a = [ 0 => [ 'period' => '2017/2018', 'product' => 'AM', 'quantity_1' => 20, 'quantity' => 25, ], 1 => [ 'period' => '2018/2019', 'product' => 'AM', 'quantity_1' => 12, 'quantity' => 19, ], 2 => [ 'period' => '2017/2018', 'product' => 'DC', 'quantity_1' => 20, 'quantity' => 25, ], 3 => [ 'period' => '2018/2019', 'product' => 'DC', 'quantity_1' => 8, 'quantity' => 10, ] ]; $temp = []; foreach ($a as $x){ $temp[$x['product']][$x['period']] = $x; } print_r($temp); $result = []; foreach ($temp as $key => $res){ $result[] = [ 'product' => $key, 'quantity_1' => $res['2018/2019']['quantity_1'] / $res['2017/2018']['quantity_1'], 'quantity_2' => $res['2018/2019']['quantity'] / $res['2017/2018']['quantity'], ]; } print_r($result);