Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/MathTrig.php
public static function logBase($number = null, $base = 10)
    {
        $number = Functions::flattenSingleValue($number);
        $base = ($base === null) ? 10 : (float) Functions::flattenSingleValue($base);

        if ((!is_numeric($base)) || (!is_numeric($number))) {
            return Functions::VALUE();
        }
        if (($base <= 0) || ($number <= 0)) {
            return Functions::NAN();
        }

        return log($number, $base);
    }
public static function logBase($number = null, $base = 10)
    {
        $number = Functions::flattenSingleValue($number);
        $base = ($base === null) ? 10 : (float) Functions::flattenSingleValue($base);

        if ((!is_numeric($base)) || (!is_numeric($number))) {
            return Functions::VALUE();
        }
        if (($base <= 0) || ($number <= 0)) {
            return Functions::NAN();
        }

        return log($number, $base);
    }
LOG_BASE.

Returns the logarithm of a number to a specified base. The default base is 10.

Excel Function:
LOG(number[,base])

@category Mathematical and Trigonometric Functions

@param float $number The positive real number for which you want the logarithm
@param float $base The base of the logarithm. If base is omitted, it is assumed to be 10.

@return float