yii\web\MultipartFormDataParser::getByteSize PHP Method

    private function getByteSize($verboseSize)
    {
        if (empty($verboseSize)) {
            return 0;
        }
        if (is_numeric($verboseSize)) {
            return (int) $verboseSize;
        }
        $sizeUnit = trim($verboseSize, '0123456789');
        $size = str_replace($sizeUnit, '', $verboseSize);
        $size = trim($size);
        if (!is_numeric($size)) {
            return 0;
        }
        switch (strtolower($sizeUnit)) {
            case 'kb':
            case 'k':
                return $size * 1024;
            case 'mb':
            case 'm':
                return $size * 1024 * 1024;
            case 'gb':
            case 'g':
                return $size * 1024 * 1024 * 1024;
            default:
                return 0;
        }
    }