Array
(
    [0] => Array
    (
        [barcode] => 48000479
        [code] => SK-1030-0049
    )

[1] => Array
    (
        [barcode] => 31145499
        [code] => SST-1000-0066
    )

)

   Array
(
   [0] => 2
   [1] => 5
)

Array
(
[0] => Array
      (
        [barcode] => 48000479
        [code] => SK-1030-0049
        [quantity] => 2
    )

[1] => Array
    (
        [barcode] => 31145499
        [code] => SST-1000-0066
        [quantity] => 5
    )

foreach($first as $k => $v) {
    $first[$k]['quantity'] = $second[$v];
}