Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Writer/Xlsx/Style.php
private function writeGradientFill(XMLWriter $objWriter, Fill $pFill)
    {
        // fill
        $objWriter->startElement('fill');

        // gradientFill
        $objWriter->startElement('gradientFill');
        $objWriter->writeAttribute('type', $pFill->getFillType());
        $objWriter->writeAttribute('degree', $pFill->getRotation());

        // stop
        $objWriter->startElement('stop');
        $objWriter->writeAttribute('position', '0');

        // color
        $objWriter->startElement('color');
        $objWriter->writeAttribute('rgb', $pFill->getStartColor()->getARGB());
        $objWriter->endElement();

        $objWriter->endElement();

        // stop
        $objWriter->startElement('stop');
        $objWriter->writeAttribute('position', '1');

        // color
        $objWriter->startElement('color');
        $objWriter->writeAttribute('rgb', $pFill->getEndColor()->getARGB());
        $objWriter->endElement();

        $objWriter->endElement();

        $objWriter->endElement();

        $objWriter->endElement();
    }
private function writeGradientFill(XMLWriter $objWriter, Fill $pFill)
    {
        // fill
        $objWriter->startElement('fill');

        // gradientFill
        $objWriter->startElement('gradientFill');
        $objWriter->writeAttribute('type', $pFill->getFillType());
        $objWriter->writeAttribute('degree', $pFill->getRotation());

        // stop
        $objWriter->startElement('stop');
        $objWriter->writeAttribute('position', '0');

        // color
        $objWriter->startElement('color');
        $objWriter->writeAttribute('rgb', $pFill->getStartColor()->getARGB());
        $objWriter->endElement();

        $objWriter->endElement();

        // stop
        $objWriter->startElement('stop');
        $objWriter->writeAttribute('position', '1');

        // color
        $objWriter->startElement('color');
        $objWriter->writeAttribute('rgb', $pFill->getEndColor()->getARGB());
        $objWriter->endElement();

        $objWriter->endElement();

        $objWriter->endElement();

        $objWriter->endElement();
    }
Write Gradient Fill.

@param XMLWriter $objWriter XML Writer
@param Fill $pFill Fill style