Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Style/NumberFormat.php
public function setFormatCode($pValue)
    {
        if ($pValue == '') {
            $pValue = self::FORMAT_GENERAL;
        }
        if ($this->isSupervisor) {
            $styleArray = $this->getStyleArray(['formatCode' => $pValue]);
            $this->getActiveSheet()->getStyle($this->getSelectedCells())->applyFromArray($styleArray);
        } else {
            $this->formatCode = $pValue;
            $this->builtInFormatCode = self::builtInFormatCodeIndex($pValue);
        }

        return $this;
    }
public function setFormatCode($pValue)
    {
        if ($pValue == '') {
            $pValue = self::FORMAT_GENERAL;
        }
        if ($this->isSupervisor) {
            $styleArray = $this->getStyleArray(['formatCode' => $pValue]);
            $this->getActiveSheet()->getStyle($this->getSelectedCells())->applyFromArray($styleArray);
        } else {
            $this->formatCode = $pValue;
            $this->builtInFormatCode = self::builtInFormatCodeIndex($pValue);
        }

        return $this;
    }
Set Format Code.

@param string $pValue see self::FORMAT_*

@return NumberFormat