class XmlEncoder

1. 8.x drupal/core/modules/serialization/lib/Drupal/serialization/Encoder/XmlEncoder.php \Drupal\serialization\Encoder\XmlEncoder
2. 8.x drupal/core/vendor/symfony/serializer/Symfony/Component/Serializer/Encoder/XmlEncoder.php \Symfony\Component\Serializer\Encoder\XmlEncoder

XmlEncoder.php in drupal/core/modules/serialization/lib/Drupal/serialization/Encoder/XmlEncoder.php

Contains \Drupal\serialization\Encoder\XmlEncoder.

XmlEncoderTest.php in drupal/core/vendor/symfony/serializer/Symfony/Component/Serializer/Tests/Encoder/XmlEncoderTest.php

class XmlEncoder extends SerializerAwareEncoder implements EncoderInterface, DecoderInterface, NormalizationAwareInterface {
  private $dom;
  private $format;
  private $rootNodeName = 'response';

  /**
   * Construct new XmlEncoder and allow to change the root node element name.
   *
   * @param string $rootNodeName
   */
  public function __construct($rootNodeName = 'response') {
    $this->rootNodeName = $rootNodeName;
  }

  /**
   * {@inheritdoc}
   */
  public function encode($data, $format, array $context = array()) {
    if ($data instanceof \DOMDocument) {
      return $data
        ->saveXML();
    }
    $xmlRootNodeName = $this
      ->resolveXmlRootName($context);
    $this->dom = new \DOMDocument();
    $this->format = $format;
    if (null !== $data && !is_scalar($data)) {
      $root = $this->dom
        ->createElement($xmlRootNodeName);
      $this->dom
        ->appendChild($root);
      $this
        ->buildXml($root, $data, $xmlRootNodeName);
    }
    else {
      $this
        ->appendNode($this->dom, $data, $xmlRootNodeName);
    }
    return $this->dom
      ->saveXML();
  }

  /**
   * {@inheritdoc}
   */
  public function decode($data, $format, array $context = array()) {
    $internalErrors = libxml_use_internal_errors(true);
    $disableEntities = libxml_disable_entity_loader(true);
    libxml_clear_errors();
    $dom = new \DOMDocument();
    $dom
      ->loadXML($data, LIBXML_NONET);
    libxml_use_internal_errors($internalErrors);
    libxml_disable_entity_loader($disableEntities);
    foreach ($dom->childNodes as $child) {
      if ($child->nodeType === XML_DOCUMENT_TYPE_NODE) {
        throw new UnexpectedValueException('Document types are not allowed.');
      }
    }
    $xml = simplexml_import_dom($dom);
    if ($error = libxml_get_last_error()) {
      throw new UnexpectedValueException($error->message);
    }
    if (!$xml
      ->count()) {
      if (!$xml
        ->attributes()) {
        return (string) $xml;
      }
      $data = array();
      foreach ($xml
        ->attributes() as $attrkey => $attr) {
        $data['@' . $attrkey] = (string) $attr;
      }
      $data['#'] = (string) $xml;
      return $data;
    }
    return $this
      ->parseXml($xml);
  }

  /**
   * Checks whether the serializer can encode to given format
   *
   * @param string $format format name
   *
   * @return Boolean
   */
  public function supportsEncoding($format) {
    return 'xml' === $format;
  }

  /**
   * Checks whether the serializer can decode from given format
   *
   * @param string $format format name
   *
   * @return Boolean
   */
  public function supportsDecoding($format) {
    return 'xml' === $format;
  }

  /**
   * Sets the root node name
   *
   * @param string $name root node name
   */
  public function setRootNodeName($name) {
    $this->rootNodeName = $name;
  }

  /**
   * Returns the root node name
   * @return string
   */
  public function getRootNodeName() {
    return $this->rootNodeName;
  }

  /**
   * @param DOMNode $node
   * @param string  $val
   *
   * @return Boolean
   */
  protected final function appendXMLString($node, $val) {
    if (strlen($val) > 0) {
      $frag = $this->dom
        ->createDocumentFragment();
      $frag
        ->appendXML($val);
      $node
        ->appendChild($frag);
      return true;
    }
    return false;
  }

  /**
   * @param DOMNode $node
   * @param string  $val
   *
   * @return Boolean
   */
  protected final function appendText($node, $val) {
    $nodeText = $this->dom
      ->createTextNode($val);
    $node
      ->appendChild($nodeText);
    return true;
  }

  /**
   * @param DOMNode $node
   * @param string  $val
   *
   * @return Boolean
   */
  protected final function appendCData($node, $val) {
    $nodeText = $this->dom
      ->createCDATASection($val);
    $node
      ->appendChild($nodeText);
    return true;
  }

  /**
   * @param DOMNode             $node
   * @param DOMDocumentFragment $fragment
   *
   * @return Boolean
   */
  protected final function appendDocumentFragment($node, $fragment) {
    if ($fragment instanceof \DOMDocumentFragment) {
      $node
        ->appendChild($fragment);
      return true;
    }
    return false;
  }

  /**
   * Checks the name is a valid xml element name
   *
   * @param string $name
   *
   * @return Boolean
   */
  protected final function isElementNameValid($name) {
    return $name && false === strpos($name, ' ') && preg_match('#^[\\pL_][\\pL0-9._-]*$#ui', $name);
  }

  /**
   * Parse the input SimpleXmlElement into an array.
   *
   * @param SimpleXmlElement $node xml to parse
   *
   * @return array
   */
  private function parseXml($node) {
    $data = array();
    if ($node
      ->attributes()) {
      foreach ($node
        ->attributes() as $attrkey => $attr) {
        $data['@' . $attrkey] = (string) $attr;
      }
    }
    foreach ($node
      ->children() as $key => $subnode) {
      if ($subnode
        ->count()) {
        $value = $this
          ->parseXml($subnode);
      }
      elseif ($subnode
        ->attributes()) {
        $value = array();
        foreach ($subnode
          ->attributes() as $attrkey => $attr) {
          $value['@' . $attrkey] = (string) $attr;
        }
        $value['#'] = (string) $subnode;
      }
      else {
        $value = (string) $subnode;
      }
      if ($key === 'item') {
        if (isset($value['@key'])) {
          if (isset($value['#'])) {
            $data[(string) $value['@key']] = $value['#'];
          }
          else {
            $data[(string) $value['@key']] = $value;
          }
        }
        else {
          $data['item'][] = $value;
        }
      }
      elseif (array_key_exists($key, $data) || $key == "entry") {
        if (false === is_array($data[$key]) || false === isset($data[$key][0])) {
          $data[$key] = array(
            $data[$key],
          );
        }
        $data[$key][] = $value;
      }
      else {
        $data[$key] = $value;
      }
    }
    return $data;
  }

  /**
   * Parse the data and convert it to DOMElements
   *
   * @param DOMNode      $parentNode
   * @param array|object $data       data
   * @param string       $xmlRootNodeName
   *
   * @return Boolean
   *
   * @throws UnexpectedValueException
   */
  private function buildXml($parentNode, $data, $xmlRootNodeName = null) {
    $append = true;
    if (is_array($data) || $data instanceof \Traversable) {
      foreach ($data as $key => $data) {

        //Ah this is the magic @ attribute types.
        if (0 === strpos($key, "@") && is_scalar($data) && $this
          ->isElementNameValid($attributeName = substr($key, 1))) {
          $parentNode
            ->setAttribute($attributeName, $data);
        }
        elseif ($key === '#') {
          $append = $this
            ->selectNodeType($parentNode, $data);
        }
        elseif (is_array($data) && false === is_numeric($key)) {

          /**
           * Is this array fully numeric keys?
           */
          if (ctype_digit(implode('', array_keys($data)))) {

            /**
             * Create nodes to append to $parentNode based on the $key of this array
             * Produces <xml><item>0</item><item>1</item></xml>
             * From array("item" => array(0,1));
             */
            foreach ($data as $subData) {
              $append = $this
                ->appendNode($parentNode, $subData, $key);
            }
          }
          else {
            $append = $this
              ->appendNode($parentNode, $data, $key);
          }
        }
        elseif (is_numeric($key) || !$this
          ->isElementNameValid($key)) {
          $append = $this
            ->appendNode($parentNode, $data, "item", $key);
        }
        else {
          $append = $this
            ->appendNode($parentNode, $data, $key);
        }
      }
      return $append;
    }
    if (is_object($data)) {
      $data = $this->serializer
        ->normalize($data, $this->format);
      if (null !== $data && !is_scalar($data)) {
        return $this
          ->buildXml($parentNode, $data, $xmlRootNodeName);
      }

      // top level data object was normalized into a scalar
      if (!$parentNode->parentNode->parentNode) {
        $root = $parentNode->parentNode;
        $root
          ->removeChild($parentNode);
        return $this
          ->appendNode($root, $data, $xmlRootNodeName);
      }
      return $this
        ->appendNode($parentNode, $data, 'data');
    }
    throw new UnexpectedValueException(sprintf('An unexpected value could not be serialized: %s', var_export($data, true)));
  }

  /**
   * Selects the type of node to create and appends it to the parent.
   *
   * @param DOMNode      $parentNode
   * @param array|object $data
   * @param string       $nodeName
   * @param string       $key
   *
   * @return Boolean
   */
  private function appendNode($parentNode, $data, $nodeName, $key = null) {
    $node = $this->dom
      ->createElement($nodeName);
    if (null !== $key) {
      $node
        ->setAttribute('key', $key);
    }
    $appendNode = $this
      ->selectNodeType($node, $data);

    // we may have decided not to append this node, either in error or if its $nodeName is not valid
    if ($appendNode) {
      $parentNode
        ->appendChild($node);
    }
    return $appendNode;
  }

  /**
   * Checks if a value contains any characters which would require CDATA wrapping.
   *
   * @param string $val
   *
   * @return Boolean
   */
  private function needsCdataWrapping($val) {
    return preg_match('/[<>&]/', $val);
  }

  /**
   * Tests the value being passed and decide what sort of element to create
   *
   * @param DOMNode $node
   * @param mixed   $val
   *
   * @return Boolean
   */
  private function selectNodeType($node, $val) {
    if (is_array($val)) {
      return $this
        ->buildXml($node, $val);
    }
    elseif ($val instanceof \SimpleXMLElement) {
      $child = $this->dom
        ->importNode(dom_import_simplexml($val), true);
      $node
        ->appendChild($child);
    }
    elseif ($val instanceof \Traversable) {
      $this
        ->buildXml($node, $val);
    }
    elseif (is_object($val)) {
      return $this
        ->buildXml($node, $this->serializer
        ->normalize($val, $this->format));
    }
    elseif (is_numeric($val)) {
      return $this
        ->appendText($node, (string) $val);
    }
    elseif (is_string($val) && $this
      ->needsCdataWrapping($val)) {
      return $this
        ->appendCData($node, $val);
    }
    elseif (is_string($val)) {
      return $this
        ->appendText($node, $val);
    }
    elseif (is_bool($val)) {
      return $this
        ->appendText($node, (int) $val);
    }
    elseif ($val instanceof \DOMNode) {
      $child = $this->dom
        ->importNode($val, true);
      $node
        ->appendChild($child);
    }
    return true;
  }

  /**
   * Get real XML root node name, taking serializer options into account.
   */
  private function resolveXmlRootName(array $context = array()) {
    return isset($context['xml_root_node_name']) ? $context['xml_root_node_name'] : $this->rootNodeName;
  }

}