$CSV = fopen("input.csv", "r");

if($CSV !== FALSE)

{
    $dlc = [];
    while(! feof($CSV))
        {
        $data = fgetcsv($CSV, 1000, ";");
        $result = preg_match_all("/DLC-[A-Z0-9]+/s", $data[20], $output_array);
        if($result) {
                $dlc = array_merge($dlc, $output_array[0]);
        }
    }
}

fclose($CSV);

$dlc = array_unique($dlc);
var_dump($dlc);