public function toArray($nullValue = null, $calculateFormulas = true, $formatData = true, $returnCellRef = false)
    {
        // Garbage collect...
        $this->garbageCollect();

        //    Identify the range that we need to extract from the worksheet
        $maxCol = $this->getHighestColumn();
        $maxRow = $this->getHighestRow();
        // Return
        return $this->rangeToArray('A1:'.$maxCol.$maxRow, $nullValue, $calculateFormulas, $formatData, $returnCellRef);
    }