Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Worksheet/ColumnIterator.php
public function resetStart($startColumn = 'A')
    {
        $startColumnIndex = Coordinate::columnIndexFromString($startColumn);
        if ($startColumnIndex > Coordinate::columnIndexFromString($this->worksheet->getHighestColumn())) {
            throw new Exception("Start column ({$startColumn}) is beyond highest column ({$this->worksheet->getHighestColumn()})");
        }

        $this->startColumnIndex = $startColumnIndex;
        if ($this->endColumnIndex < $this->startColumnIndex) {
            $this->endColumnIndex = $this->startColumnIndex;
        }
        $this->seek($startColumn);

        return $this;
    }
public function resetStart($startColumn = 'A')
    {
        $startColumnIndex = Coordinate::columnIndexFromString($startColumn);
        if ($startColumnIndex > Coordinate::columnIndexFromString($this->worksheet->getHighestColumn())) {
            throw new Exception("Start column ({$startColumn}) is beyond highest column ({$this->worksheet->getHighestColumn()})");
        }

        $this->startColumnIndex = $startColumnIndex;
        if ($this->endColumnIndex < $this->startColumnIndex) {
            $this->endColumnIndex = $this->startColumnIndex;
        }
        $this->seek($startColumn);

        return $this;
    }
(Re)Set the start column and the current column pointer.

@param string $startColumn The column address at which to start iterating

@throws Exception

@return ColumnIterator