Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Statistical.php
public static function MODE(...$args)
    {
        $returnValue = Functions::NA();

        // Loop through arguments
        $aArgs = Functions::flattenArray($args);

        $mArgs = [];
        foreach ($aArgs as $arg) {
            // Is it a numeric value?
            if ((is_numeric($arg)) && (!is_string($arg))) {
                $mArgs[] = $arg;
            }
        }

        if (!empty($mArgs)) {
            return self::modeCalc($mArgs);
        }

        return $returnValue;
    }
public static function MODE(...$args)
    {
        $returnValue = Functions::NA();

        // Loop through arguments
        $aArgs = Functions::flattenArray($args);

        $mArgs = [];
        foreach ($aArgs as $arg) {
            // Is it a numeric value?
            if ((is_numeric($arg)) && (!is_string($arg))) {
                $mArgs[] = $arg;
            }
        }

        if (!empty($mArgs)) {
            return self::modeCalc($mArgs);
        }

        return $returnValue;
    }
MODE.

Returns the most frequently occurring, or repetitive, value in an array or range of data

Excel Function:
MODE(value1[,value2[, ...]])

@category Statistical Functions

@param mixed ...$args Data values

@return float