Piwik\DataTable\Renderer\Csv::formatFormulas PHP Метод

    protected function formatFormulas($value)
    {
        // Excel / Libreoffice formulas may start with one of these characters
        $formulaStartsWith = array('=', '+', '-', '@');
        // remove first % sign and if string is still a number, return it as is
        $valueWithoutFirstPercentSign = $this->removeFirstPercentSign($value);
        if (empty($valueWithoutFirstPercentSign) || !is_string($value) || is_numeric($valueWithoutFirstPercentSign)) {
            return $value;
        }
        $firstCharCellValue = $valueWithoutFirstPercentSign[0];
        $isFormula = in_array($firstCharCellValue, $formulaStartsWith);
        if ($isFormula) {
            return "'" . $value;
        }
        return $value;
    }