public function shiftColumn($fromColumn, $toColumn)
    {
        $fromColumn = strtoupper($fromColumn);
        $toColumn = strtoupper($toColumn);

        if (($fromColumn !== null) && (isset($this->columns[$fromColumn])) && ($toColumn !== null)) {
            $this->columns[$fromColumn]->setParent();
            $this->columns[$fromColumn]->setColumnIndex($toColumn);
            $this->columns[$toColumn] = $this->columns[$fromColumn];
            $this->columns[$toColumn]->setParent($this);
            unset($this->columns[$fromColumn]);

            ksort($this->columns);
        }

        return $this;
    }