Скрипт после скачивания картинки не открывает его, в чем причина?

 require "db.php";

if (isset($_GET['id'])) {
    $id = $_GET['id'];

    $sql = "SELECT * FROM 3_images WHERE id=?";
    $stmt = $db->prepare($sql);
    $stmt->bind_param("i", $id);
    $stmt->execute();
    $result = $stmt->get_result();

    if ($result->num_rows > 0) {
        $row = $result->fetch_assoc();
        $filename = 'upload/' . $row["img"];

        if (file_exists($filename)) {
            $finfo = finfo_open('jpg', 'jpeg', 'png', 'gif');
            $mime_type = finfo_file($finfo, $filename);
            finfo_close($finfo);

            header('Content-Description: File Transfer');
            header('Content-Type: ' . $mime_type);
            header('Content-Disposition: attachment; filename="'.basename($filename).'"');
            header('Expires: 0');
            header('Cache-Control: must-revalidate');
            header('Pragma: public');
            header('Content-Length: ' . filesize($filename));
            readfile($filename);
            exit;
        } else {
            echo "The file $filename does not exist.";
        }
    } else {
        echo "No record matches the provided id.";
    }
} else {
    echo "No id provided.";
}
?>