framework/web/XmlResponseFormatter.php
protected function formatScalarValue($value)
    {
        if ($value === true) {
            return 'true';
        }
        if ($value === false) {
            return 'false';
        }
        if (is_float($value)) {
            return StringHelper::floatToString($value);
        }
        return (string) $value;
    }
protected function formatScalarValue($value)
    {
        if ($value === true) {
            return 'true';
        }
        if ($value === false) {
            return 'false';
        }
        if (is_float($value)) {
            return StringHelper::floatToString($value);
        }
        return (string) $value;
    }
Formats scalar value to use in XML text node.

@param int|string|bool|float $value a scalar value.
@return string string representation of the value.
@since 2.0.11