if ((isset($_GET['database'])) && (isset($_GET['database2'])) && (isset($_GET['support'])) && (isset($_GET['confidence'])))
{
    $database = $_GET['database'];
    $database2 = $_GET['database2'];
    $support = $_GET['support'];
    $confidence = $_GET['confidence'];
    .
    .
    .// I just enter the code that I think is important.
    .
    .
    if ($mysqli->connect_errno)
    {
        printf("Connect failed: %sn", $mysqli->connect_error);
        exit();
    }

    if ($result = $mysqli->query("SELECT product_name FROM `tbl_transaction` WHERE idimport_database = '$database'&&'$database2' GROUP BY idproduct", MYSQLI_USE_RESULT))
    {
        while ($i = $result->fetch_row())
        {
            $item[] = $i[0];
        }
        $result->close();
    }

    if ($result = $mysqli->query("  select group_concat(tbl_transaction.product_name separator ',')
        from tbl_transaction
        WHERE idimport_database = '$database'&&'$database2'
        group by tbl_transaction.no_transaction", MYSQLI_USE_RESULT))
    {
        while ($b = $result->fetch_row())
        {
            $belian[] = $b[0];
        }
        $result->close();
    }
    $mysqli->close();