Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Engineering.php
public static function IMLOG10($complexNumber)
    {
        $complexNumber = Functions::flattenSingleValue($complexNumber);

        $parsedComplex = self::parseComplex($complexNumber);

        if (($parsedComplex['real'] == 0.0) && ($parsedComplex['imaginary'] == 0.0)) {
            return Functions::NAN();
        } elseif (($parsedComplex['real'] > 0.0) && ($parsedComplex['imaginary'] == 0.0)) {
            return log10($parsedComplex['real']);
        }

        return self::IMPRODUCT(log10(self::EULER), self::IMLN($complexNumber));
    }
public static function IMLOG10($complexNumber)
    {
        $complexNumber = Functions::flattenSingleValue($complexNumber);

        $parsedComplex = self::parseComplex($complexNumber);

        if (($parsedComplex['real'] == 0.0) && ($parsedComplex['imaginary'] == 0.0)) {
            return Functions::NAN();
        } elseif (($parsedComplex['real'] > 0.0) && ($parsedComplex['imaginary'] == 0.0)) {
            return log10($parsedComplex['real']);
        }

        return self::IMPRODUCT(log10(self::EULER), self::IMLN($complexNumber));
    }
IMLOG10.

Returns the common logarithm (base 10) of a complex number in x + yi or x + yj text format.

Excel Function:
IMLOG10(complexNumber)

@param string $complexNumber the complex number for which you want the common logarithm

@return string