Format::to_xml PHP Method

    public function to_xml($data = NULL, $structure = NULL, $basenode = 'xml')
    {
        if ($data === NULL && func_num_args() === 0) {
            $data = $this->_data;
        }
        if ($structure === NULL) {
            $structure = simplexml_load_string("<?xml version='1.0' encoding='utf-8'?><{$basenode} />");
        }
        // Force it to be something useful
        if (is_array($data) === FALSE && is_object($data) === FALSE) {
            $data = (array) $data;
        }
        foreach ($data as $key => $value) {
            //change false/true to 0/1
            if (is_bool($value)) {
                $value = (int) $value;
            }
            // no numeric keys in our xml please!
            if (is_numeric($key)) {
                // make string key...
                $key = singular($basenode) != $basenode ? singular($basenode) : 'item';
            }
            // replace anything not alpha numeric
            $key = preg_replace('/[^a-z_\\-0-9]/i', '', $key);
            if ($key === '_attributes' && (is_array($value) || is_object($value))) {
                $attributes = $value;
                if (is_object($attributes)) {
                    $attributes = get_object_vars($attributes);
                }
                foreach ($attributes as $attribute_name => $attribute_value) {
                    $structure->addAttribute($attribute_name, $attribute_value);
                }
            } elseif (is_array($value) || is_object($value)) {
                $node = $structure->addChild($key);
                // recursive call.
                $this->to_xml($value, $node, $key);
            } else {
                // add single node.
                $value = htmlspecialchars(html_entity_decode($value, ENT_QUOTES, 'UTF-8'), ENT_QUOTES, 'UTF-8');
                $structure->addChild($key, $value);
            }
        }
        return $structure->asXML();
    }