Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
private function writeString($row, $col, $str, $xfIndex)
    {
        $this->writeLabelSst($row, $col, $str, $xfIndex);
    }
private function writeString($row, $col, $str, $xfIndex)
    {
        $this->writeLabelSst($row, $col, $str, $xfIndex);
    }
Write a LABELSST record or a LABEL record. Which one depends on BIFF version.

@param int $row Row index (0-based)
@param int $col Column index (0-based)
@param string $str The string
@param int $xfIndex Index to XF record