PHP7 possible compatibility issue

You probably want to read this https://wiki.php.net/rfc/uniform_variable_syntax

No, sorry that looks like its probably correct without the context of the original code. Just wanted to link to the documentation for why it was failing to make sure it was being resolved correctly.

Needs a patch.

Using this as my guide: https://blog.engineyard.com/2015/what-to-expect-php-7

This patch covers all the ->$

@joelpittet thanks. Just to confirm, is this patch tested on PHP7?

@amitaibu yes:) Got php70 running with homebrew yesterday to give it a spin, that's why I'm here;)

1. +++ b/includes/message.admin.inc
   @@ -21,7 +21,7 @@ class MessageTypeUIController extends EntityDefaultUIController {
   -        $entity->$key = $value;
   +        $entity->{$key} = $value;
   
   +++ b/includes/views/handlers/message_handler_field_message_render.inc
   @@ -72,7 +72,7 @@ class message_handler_field_message_render extends views_handler_field {
   -    if (!empty($values->$field_alias) && $message = message_load($values->$field_alias)) {
   +    if (!empty($values->{$field_alias}) && $message = message_load($values->{$field_alias})) {
   

   These should resolve the same. The change in 7 was order of operations but there's nothing like that going on here.

2. +++ b/message.module
   @@ -513,7 +513,7 @@ function _message_delete_messages($field_names, $entity_id, $last_mid = 0, $rang
   -          if ($wrapper->$field_name->get($i)->value()) {
   +          if ($wrapper->{$field_name}->get($i)->value()) {
   

   If I'm reading this correctly this should resolve the same too.

   https://3v4l.org/CBZtU

Yes @neclimdul you are right, though does it hurt to be explicit and consistent everywhere?

@ryan weal it did! It was fat along out and after that it let me use php7.

Not all of the patch is nessasary I just covered everything with the same explicit fix.

merged, thanks.

btw, I'm about to soon close this issue queue in favor of the GitHub one

A new release will be published shortly :)

Patch #7 works very well - big thanks :)
I was surprised to see usage of variables without { } :O Anyway, someone could put this into official version, because I think currently more and more people will update PHP version :)

It is already part of Message - https://www.drupal.org/node/2639122

Right, my bad :) I thought one of my coworkers has made updates since Decemeber - guess I was wrong. Sorry for misunderstanding :D

Can anybody help patch this code, I am getting an error EntityMetadataWrapperException : Unknown data property Array. In EntityStructureWrapper->getPropertyInfo() (line 354 in entity.wrapper.inc), I am pasting the code from entity wrapper here, I have PHP 7. Trying the patch bracket on line 353, fixes the problem but right after the site breaks with an illegal syntax error referring to the modified line. The code is also availabe in the attached text file.

<?php

/**
 * @file
 * Provides wrappers allowing easy usage of the entity metadata.
 */

/**
 * A common base class for all wrappers.
 */
abstract class EntityMetadataWrapper {

  protected $type;
  protected $data;
  protected $info;
  protected $cache = array();

  /**
   * Construct a new wrapper object.
   *
   * @param $type
   *   The type of the passed data.
   * @param $data
   *   Optional. The data to wrap.
   * @param $info
   *   Optional. Used internally to pass info about properties down the tree.
   */
  public function __construct($type, $data = NULL, $info = array()) {
    $this->type = $type;
    $this->info = $info + array(
      'langcode' => NULL,
    );
    $this->info['type'] = $type;
    if (isset($data)) {
      $this->set($data);
    }
  }

  /**
   * Gets info about the wrapped data.
   *
   * @return Array
   *   Keys set are all keys as specified for a property in hook_entity_info()
   *   as well as possible the following keys:
   *    - name: If this wraps a property, the name of the property.
   *    - parent: The parent wrapper, if any.
   *    - langcode: The language code, if this data is language specific.
   */
  public function info() {
    return $this->info;
  }

  /**
   * Gets the (entity)type of the wrapped data.
   */
  public function type() {
    return $this->type;
  }

  /**
   * Returns the wrapped data. If no options are given the data is returned as
   * described in the info.
   *
   * @param $options
   *   (optional) A keyed array of options:
   *   - sanitize: A boolean flag indicating that textual properties should be
   *     sanitized for display to a web browser. Defaults to FALSE.
   *   - decode: If set to TRUE and some textual data is already sanitized, it
   *     strips HTML tags and decodes HTML entities. Defaults to FALSE.
   *
   *  @return
   *    The value of the wrapped data. If the data property is not set, NULL
   *    is returned.
   *
   *  @throws EntityMetadataWrapperException
   *    In case there are no data values available to the wrapper, an exception
   *    is thrown. E.g. if the value for an entity property is to be retrieved
   *    and there is no entity available, the exception is thrown. However, if
   *    an entity is available but the property is not set, NULL is returned.
   */
  public function value(array $options = array()) {
    if (!$this->dataAvailable() && isset($this->info['parent'])) {
      throw new EntityMetadataWrapperException('Missing data values.');
    }
    if (!isset($this->data) && isset($this->info['name'])) {
      $this->data = $this->info['parent']->getPropertyValue($this->info['name'], $this->info);
    }
    return $this->data;
  }

  /**
   * Returns the raw, unprocessed data. Most times this is the same as returned
   * by value(), however for already processed and sanitized textual data, this
   * will return the unprocessed data in contrast to value().
   */
  public function raw() {
    if (!$this->dataAvailable()) {
      throw new EntityMetadataWrapperException('Missing data values.');
    }
    if (isset($this->info['name']) && isset($this->info['parent'])) {
      return $this->info['parent']->getPropertyRaw($this->info['name'], $this->info);
    }
    // Else return the usual value, which should be raw in this case.
    return $this->value();
  }

  /**
   * Returns whether data is available to work with.
   *
   * @return
   *   If we operate without any data FALSE, else TRUE.
   */
  protected function dataAvailable() {
    return isset($this->data) || (isset($this->info['parent']) && $this->info['parent']->dataAvailable());
  }

  /**
   * Set a new data value.
   */
  public function set($value) {
    if (!$this->validate($value)) {
      throw new EntityMetadataWrapperException(t('Invalid data value given. Be sure it matches the required data type and format. Value at !location: !value.', array(
        // An exception's message is output through check_plain().
        '!value' => is_array($value) || is_object($value) ? var_export($value, TRUE) : $value,
        '!location' => $this->debugIdentifierLocation(),
      )));
    }
    $this->clear();
    $this->data = $value;
    $this->updateParent($value);
    return $this;
  }

  /**
   * Updates the parent data structure of a data property with the latest data value.
   */
  protected function updateParent($value) {
    if (isset($this->info['parent'])) {
      $this->info['parent']->setProperty($this->info['name'], $value);
    }
  }

  /**
   * Returns whether $value is a valid value to set.
   */
  public function validate($value) {
    if (isset($value) && !entity_property_verify_data_type($value, $this->type)) {
      return FALSE;
    }
    // Only proceed with further checks if this is not a list item. If this is
    // a list item, the checks are performed on the list property level.
    if (isset($this->info['parent']) && $this->info['parent'] instanceof EntityListWrapper) {
      return TRUE;
    }
    if (!isset($value) && !empty($this->info['required'])) {
      // Do not allow NULL values if the property is required.
      return FALSE;
    }
    return !isset($this->info['validation callback']) || call_user_func($this->info['validation callback'], $value, $this->info);
  }

  public function __toString() {
    return isset($this->info) ? 'Property ' . $this->info['name'] : $this->type;
  }

  /**
   * Clears the data value and the wrapper cache.
   */
  protected function clear() {
    $this->data = NULL;
    foreach ($this->cache as $wrapper) {
      $wrapper->clear();
    }
  }

  /**
   * Returns the options list specifying possible values for the property, if
   * defined.
   *
   * @param $op
   *   (optional) One of 'edit' or 'view'. In case the list of possible values
   *   a user could set for a property differs from the list of values a
   *   property could have, $op determines which options should be returned.
   *   Defaults to 'edit'.
   *   E.g. all possible roles a user could have include the anonymous and the
   *   authenticated user roles, while those roles cannot be added to a user
   *   account. So their options would be included for 'view', but for 'edit'
   *   not.
   *
   * @return
   *   An array as used by hook_options_list() or FALSE.
   */
  public function optionsList($op = 'edit') {
    if (isset($this->info['options list']) && is_callable($this->info['options list'])) {
      $name = isset($this->info['name']) ? $this->info['name'] : NULL;
      return call_user_func($this->info['options list'], $name, $this->info, $op);
    }
    return FALSE;
  }

  /**
   * Returns the label for the currently set property value if there is one
   * available, i.e. if an options list has been specified.
   */
  public function label() {
    if ($options = $this->optionsList('view')) {
      $options = entity_property_options_flatten($options);
      $value = $this->value();
      if (is_scalar($value) && isset($options[$value])) {
        return $options[$value];
      }
    }
  }

  /**
   * Determines whether the given user has access to view or edit this property.
   * Apart from relying on access metadata of properties, this takes into
   * account information about entity level access, if available:
   *  - Referenced entities can only be viewed, when the user also has
   *    permission to view the entity.
   *  - A property may be only edited, if the user has permission to update the
   *    entity containing the property.
   *
   * @param $op
   *   The operation being performed. One of 'view' or 'edit.
   * @param $account
   *   The user to check for. Leave it to NULL to check for the global user.
   * @return boolean
   *   Whether access to entity property is allowed for the given operation.
   *   However if we wrap no data, it returns whether access is allowed to the
   *   property of all entities of this type.
   *   If there is no access information for this property, TRUE is returned.
   */
  public function access($op, $account = NULL) {
    return !empty($this->info['parent']) ? $this->info['parent']->propertyAccess($this->info['name'], $op, $account) : TRUE;
  }

  /**
   * Returns a string to use to identify this wrapper in error messages.
   *
   * @return
   *  A string that identifies this wrapper and its chain of ancestors, of the
   *  form 'grandparentidentifier->parentidentifier->identifier'.
   */
  public function debugIdentifierLocation() {
    $debug = $this->info['name'];
    if (isset($this->info['parent'])) {
      $debug = $this->info['parent']->debugIdentifierLocation() . '->' . $debug;
    }
    return $debug;
  }

  /**
   * Prepare for serializiation.
   */
  public function __sleep() {
    $vars = get_object_vars($this);
    unset($vars['cache']);
    return drupal_map_assoc(array_keys($vars));
  }
}

/**
 * Wraps a single value.
 */
class EntityValueWrapper extends EntityMetadataWrapper {

  /**
   * Overrides EntityMetadataWrapper#value().
   * Sanitizes or decode textual data if necessary.
   */
  public function value(array $options = array()) {
    $data = parent::value();
    if ($this->type == 'text' && isset($data)) {
      $info = $this->info + array('sanitized' => FALSE, 'sanitize' => 'check_plain');
      $options += array('sanitize' => FALSE, 'decode' => FALSE);
      if ($options['sanitize'] && !$info['sanitized']) {
        return call_user_func($info['sanitize'], $data);
      }
      elseif ($options['decode'] && $info['sanitized']) {
        return decode_entities(strip_tags($data));
      }
    }
    return $data;
  }
}

/**
 * Provides a general wrapper for any data structure. For this to work the
 * metadata has to be passed during construction.
 */
class EntityStructureWrapper extends EntityMetadataWrapper implements IteratorAggregate {

  protected $propertyInfo = array(), $propertyInfoAltered = FALSE;
  protected $langcode = LANGUAGE_NONE;

  protected $propertyInfoDefaults = array(
    'type' => 'text',
    'getter callback' => 'entity_property_verbatim_get',
    'clear' => array(),
  );

  /**
   * Construct a new EntityStructureWrapper object.
   *
   * @param $type
   *   The type of the passed data.
   * @param $data
   *   Optional. The data to wrap.
   * @param $info
   *   Used to for specifying metadata about the data and internally to pass
   *   info about properties down the tree. For specifying metadata known keys
   *   are:
   *   - property info: An array of info about the properties of the wrapped
   *     data structure. It has to contain an array of property info in the same
   *     structure as used by hook_entity_property_info().
   */
  public function __construct($type, $data = NULL, $info = array()) {
    parent::__construct($type, $data, $info);
    $this->info += array('property defaults' => array());
    $info += array('property info' => array());
    $this->propertyInfo['properties'] = $info['property info'];
  }

  /**
   * May be used to lazy-load additional info about the data, depending on the
   * concrete passed data.
   */
  protected function spotInfo() {
    // Apply the callback if set, such that the caller may alter the info.
    if (!empty($this->info['property info alter']) && !$this->propertyInfoAltered) {
      $this->propertyInfo = call_user_func($this->info['property info alter'], $this, $this->propertyInfo);
      $this->propertyInfoAltered = TRUE;
    }
  }

  /**
   * Gets the info about the given property.
   *
   * @param $name
   *   The name of the property. If not given, info about all properties will
   *   be returned.
   * @throws EntityMetadataWrapperException
   *   If there is no such property.
   * @return
   *   An array of info about the property.
   */
  public function getPropertyInfo($name = NULL) {
    $this->spotInfo();
    if (!isset($name)) {
      return $this->{propertyInfo['properties']};
    }
    if (!isset($this->propertyInfo['properties'][$name])) {
      throw new EntityMetadataWrapperException('Unknown data property ' . check_plain($name) . '.');
    }
    return $this->propertyInfo['properties'][$name] + $this->info['property defaults'] + $this->propertyInfoDefaults;
  }

  /**
   * Returns a reference on the property info.
   *
   * If possible, use the property info alter callback for spotting metadata.
   * The reference may be used to alter the property info for any remaining
   * cases, e.g. if additional metadata has been asserted.
   */
  public function &refPropertyInfo() {
    return $this->propertyInfo;
  }

  /**
   * Sets a new language to use for retrieving properties.
   *
   * @param $langcode
   *   The language code of the language to set.
   * @return EntityWrapper
   */
  public function language($langcode = LANGUAGE_NONE) {
    if ($langcode != $this->langcode) {
      $this->langcode = $langcode;
      $this->cache = array();
    }
    return $this;
  }

  /**
   * Gets the language used for retrieving properties.
   *
   * @return String
   *   The language object of the language or NULL for the default language.
   *
   * @see EntityStructureWrapper::language()
   */
  public function getPropertyLanguage() {
    if ($this->langcode != LANGUAGE_NONE && $list = language_list()) {
      if (isset($list[$this->langcode])) {
        return $list[$this->langcode];
      }
    }
    return NULL;
  }

  /**
   * Get the wrapper for a property.
   *
   * @return
   *   An instance of EntityMetadataWrapper.
   */
  public function get($name) {
    // Look it up in the cache if possible.
    if (!array_key_exists($name, $this->cache)) {
      if ($info = $this->getPropertyInfo($name)) {
        $info += array('parent' => $this, 'name' => $name, 'langcode' => $this->langcode, 'property defaults' => array());
        $info['property defaults'] += $this->info['property defaults'];
        $this->cache[$name] = entity_metadata_wrapper($info['type'], NULL, $info);
      }
      else {
        throw new EntityMetadataWrapperException('There is no property ' . check_plain($name) . " for this entity.");
      }
    }
    return $this->cache[$name];
  }

  /**
   * Magic method: Get a wrapper for a property.
   */
  public function __get($name) {
    if (strpos($name, 'krumo') === 0) {
      // #914934 Ugly workaround to allow krumo to write its recursion property.
      // This is necessary to make dpm() work without throwing exceptions.
      return NULL;
    }
    $get = $this->get($name);
    return $get;
  }

  /**
   * Magic method: Set a property.
   */
  public function __set($name, $value) {
    if (strpos($name, 'krumo') === 0) {
      // #914934 Ugly workaround to allow krumo to write its recursion property.
      // This is necessary to make dpm() work without throwing exceptions.
      $this->$name = $value;
    }
    else {
      $this->get($name)->set($value);
    }
  }

  /**
   * Gets the value of a property.
   */
  protected function getPropertyValue($name, &$info) {
    $options = array('language' => $this->getPropertyLanguage(), 'absolute' => TRUE);
    $data = $this->value();
    if (!isset($data)) {
      throw new EntityMetadataWrapperException('Unable to get the data property ' . check_plain($name) . ' as the parent data structure is not set.');
    }
    return $info['getter callback']($data, $options, $name, $this->type, $info);
  }

  /**
   * Gets the raw value of a property.
   */
  protected function getPropertyRaw($name, &$info) {
    if (!empty($info['raw getter callback'])) {
      $options = array('language' => $this->getPropertyLanguage(), 'absolute' => TRUE);
      $data = $this->value();
      if (!isset($data)) {
        throw new EntityMetadataWrapperException('Unable to get the data property ' . check_plain($name) . ' as the parent data structure is not set.');
      }
      return $info['raw getter callback']($data, $options, $name, $this->type, $info);
    }
    return $this->getPropertyValue($name, $info);
  }

  /**
   * Sets a property.
   */
  protected function setProperty($name, $value) {
    $info = $this->getPropertyInfo($name);
    if (!empty($info['setter callback'])) {
      $data = $this->value();

      // In case the data structure is not set, support simple auto-creation
      // for arrays. Else an exception is thrown.
      if (!isset($data)) {
        if (!empty($this->info['auto creation']) && !($this instanceof EntityDrupalWrapper)) {
          $data = $this->info['auto creation']($name, $this->info);
        }
        else {
          throw new EntityMetadataWrapperException('Unable to set the data property ' . check_plain($name) . ' as the parent data structure is not set.');
        }
      }

      // Invoke the setter callback for updating our data.
      $info['setter callback']($data, $name, $value, $this->langcode, $this->type, $info);

      // If the setter has not thrown any exceptions, proceed and apply the
      // update to the current and any parent wrappers as necessary.
      $data = $this->info['type'] == 'entity' ? $this : $data;
      $this->set($data);

      // Clear the cache of properties dependent on this value.
      foreach ($info['clear'] as $name) {
        if (isset($this->cache[$name])) {
          $this->cache[$name]->clear();
        }
      }
    }
    else {
      throw new EntityMetadataWrapperException('Entity property ' . check_plain($name) . " doesn't support writing.");
    }
  }

  protected function propertyAccess($name, $op, $account = NULL) {
    $info = $this->getPropertyInfo($name);

    // If a property should be edited and this is part of an entity, make sure
    // the user has update access for this entity.
    if ($op == 'edit') {
      $entity = $this;
      while (!($entity instanceof EntityDrupalWrapper) && isset($entity->info['parent'])) {
        $entity = $entity->info['parent'];
      }
      if ($entity instanceof EntityDrupalWrapper && $entity->entityAccess('update', $account) === FALSE) {
        return FALSE;
      }
    }
    if (!empty($info['access callback'])) {
      $data = $this->dataAvailable() ? $this->value() : NULL;
      return call_user_func($info['access callback'], $op, $name, $data, $account, $this->type);
    }
    elseif ($op == 'edit' && isset($info['setter permission'])) {
      return user_access($info['setter permission'], $account);
    }
    // If access is unknown, we return TRUE.
    return TRUE;
  }

  /**
   * Magic method: Can be used to check if a property is known.
   */
  public function __isset($name) {
    $this->spotInfo();
    return isset($this->propertyInfo['properties'][$name]);
  }

  public function getIterator() {
    $this->spotInfo();
    return new EntityMetadataWrapperIterator($this, array_keys($this->propertyInfo['properties']));
  }

  /**
   * Returns the identifier of the data structure. If there is none, NULL is
   * returned.
   */
  public function getIdentifier() {
    return isset($this->id) && $this->dataAvailable() ? $this->id->value() : NULL;
  }

  /**
   * Prepare for serializiation.
   */
  public function __sleep() {
    $vars = parent::__sleep();
    unset($vars['propertyInfoDefaults']);
    return $vars;
  }

  public function clear() {
    $this->propertyInfoAltered = FALSE;
    parent::clear();
  }
}

/**
 * Provides a wrapper for entities registrered in hook_entity_info().
 *
 * The wrapper eases applying getter and setter callbacks of entity properties
 * specified in hook_entity_property_info().
 */
class EntityDrupalWrapper extends EntityStructureWrapper {

  /**
   * Contains the entity id.
   */
  protected $id = FALSE;
  protected $bundle;
  protected $entityInfo;

  /**
   * Construct a new EntityDrupalWrapper object.
   *
   * @param $type
   *   The type of the passed data.
   * @param $data
   *   Optional. The entity to wrap or its identifier.
   * @param $info
   *   Optional. Used internally to pass info about properties down the tree.
   */
  public function __construct($type, $data = NULL, $info = array()) {
    parent::__construct($type, $data, $info);
    $this->setUp();
  }

  protected function setUp() {
    $this->propertyInfo = entity_get_property_info($this->type) + array('properties' => array());
    $info = $this->info + array('property info' => array(), 'bundle' => NULL);
    $this->propertyInfo['properties'] += $info['property info'];
    $this->bundle = $info['bundle'];
    $this->entityInfo = entity_get_info($this->type);
    if (isset($this->bundle)) {
      $this->spotBundleInfo(FALSE);
    }
  }

  /**
   * Sets the entity internally accepting both the entity id and object.
   */
  protected function setEntity($data) {
    // For entities we allow getter callbacks to return FALSE, which we
    // interpret like NULL values as unset properties.
    if (isset($data) && $data !== FALSE && !is_object($data)) {
      $this->id = $data;
      $this->data = FALSE;
    }
    elseif (is_object($data) && $data instanceof EntityDrupalWrapper) {
      // We got a wrapped entity passed, so take over its values.
      $this->id = $data->id;
      $this->data = $data->data;
      // For generic entity references, also update the entity type accordingly.
      if ($this->info['type'] == 'entity') {
        $this->type = $data->type;
      }
    }
    elseif (is_object($data)) {
      // We got the entity object passed.
      $this->data = $data;
      $id = entity_id($this->type, $data);
      $this->id = isset($id) ? $id : FALSE;
    }
    else {
      $this->id = FALSE;
      $this->data = NULL;
    }
  }

  /**
   * Used to lazy-load bundle info. So the wrapper can be loaded e.g. just
   * for setting without the data being loaded.
   */
  protected function spotInfo() {
    if (!$this->propertyInfoAltered) {
      if ($this->info['type'] == 'entity' && $this->dataAvailable() && $this->value()) {
        // Add in entity-type specific details.
        $this->setUp();
      }
      $this->spotBundleInfo(TRUE);
      parent::spotInfo();
      $this->propertyInfoAltered = TRUE;
    }
  }

  /**
   * Tries to determine the bundle and adds in the according property info.
   *
   * @param $load
   *   Whether the entity should be loaded to spot the info if necessary.
   */
  protected function spotBundleInfo($load = TRUE) {
    // Like entity_extract_ids() assume the entity type if no key is given.
    if (empty($this->entityInfo['entity keys']['bundle']) && $this->type != 'entity') {
      $this->bundle = $this->type;
    }
    // Detect the bundle if not set yet and add in properties from the bundle.
    elseif (!$this->bundle && $load && $this->dataAvailable()) {
      try {
        if ($entity = $this->value()) {
          list($id, $vid, $bundle) = entity_extract_ids($this->type, $entity);
          $this->bundle = $bundle;
        }
      }
      catch (EntityMetadataWrapperException $e) {
        // Loading data failed, so we cannot derive the used bundle.
      }
    }

    if ($this->bundle && isset($this->propertyInfo['bundles'][$this->bundle])) {
      $bundle_info = (array) $this->propertyInfo['bundles'][$this->bundle] + array('properties' => array());
      // Allow bundles to re-define existing properties, such that the bundle
      // can add in more bundle-specific details like the bundle of a referenced
      // entity.
      $this->propertyInfo['properties'] = $bundle_info['properties'] + $this->propertyInfo['properties'];
    }
  }

  /**
   * Returns the identifier of the wrapped entity.
   *
   * @see entity_id()
   */
  public function getIdentifier() {
    return $this->dataAvailable() ? $this->value(array('identifier' => TRUE)) : NULL;
  }

  /**
   * Returns the bundle of an entity, or FALSE if it has no bundles.
   */
  public function getBundle() {
    if ($this->dataAvailable()) {
      $this->spotInfo();
      return $this->bundle;
    }
  }

  /**
   * Overridden.
   *
   * @param $options
   *   An array of options. Known keys:
   *   - identifier: If set to TRUE, the entity identifier is returned.
   */
  public function value(array $options = array()) {
    // Try loading the data via the getter callback if there is none yet.
    if (!isset($this->data)) {
      $this->setEntity(parent::value());
    }
    if (!empty($options['identifier'])) {
      return $this->id;
    }
    elseif (!$this->data && !empty($this->id)) {
      // Lazy load the entity if necessary.
      $return = entity_load($this->type, array($this->id));
      // In case the entity cannot be loaded, we return NULL just as for empty
      // properties.
      $this->data = $return ? reset($return) : NULL;
    }
    return $this->data;
  }

  /**
   * Returns the entity prepared for rendering.
   *
   * @see entity_view()
   */
  public function view($view_mode = 'full', $langcode = NULL, $page = NULL) {
    return entity_view($this->type(), array($this->value()), $view_mode, $langcode, $page);
  }

  /**
   * Overridden to support setting the entity by either the object or the id.
   */
  public function set($value) {
    if (!$this->validate($value)) {
      throw new EntityMetadataWrapperException(t('Invalid data value given. Be sure it matches the required data type and format. Value at !location: !value.', array(
        // An exception's message is output through check_plain().
        '!value' => is_array($value) || is_object($value) ? var_export($value, TRUE) : $value,
        '!location' => $this->debugIdentifierLocation(),
      )));
    }
    if ($this->info['type'] == 'entity' && $value === $this) {
      // Nothing to do.
      return $this;
    }
    $previous_id = $this->id;
    $previous_type = $this->type;
    // Set value, so we get the identifier and pass it to the normal setter.
    $this->clear();
    $this->setEntity($value);
    // Generally, we have to update the parent only if the entity reference
    // has changed. In case of a generic entity reference, we pass the entity
    // wrapped. Else we just pass the id of the entity to the setter callback.
    if ($this->info['type'] == 'entity' && ($previous_id != $this->id || $previous_type != $this->type)) {
      // We need to clone the wrapper we pass through as value, so it does not
      // get cleared when the current wrapper instance gets cleared.
      $this->updateParent(clone $this);
    }
    // In case the entity has been unset, we cannot properly detect changes as
    // the previous id defaults to FALSE for unloaded entities too. So in that
    // case we just always update the parent.
    elseif ($this->id === FALSE && !$this->data) {
      $this->updateParent(NULL);
    }
    elseif ($previous_id !== $this->id) {
      $this->updateParent($this->id);
    }
    return $this;
  }

  /**
   * Overridden.
   */
  public function clear() {
    $this->id = NULL;
    $this->bundle = isset($this->info['bundle']) ? $this->info['bundle'] : NULL;
    if ($this->type != $this->info['type']) {
      // Reset entity info / property info based upon the info provided during
      // the creation of the wrapper.
      $this->type = $this->info['type'];
      $this->setUp();
    }
    parent::clear();
  }

  /**
   * Overridden.
   */
  public function type() {
    // In case of a generic entity wrapper, load the data first to determine
    // the type of the concrete entity.
    if ($this->dataAvailable() && $this->info['type'] == 'entity') {
      try {
        $this->value(array('identifier' => TRUE));
      }
      catch (EntityMetadataWrapperException $e) {
        // If loading data fails, we cannot determine the concrete entity type.
      }
    }
    return $this->type;
  }

  /**
   * {@inheritdoc}
   *
   * Note that this method checks property access, but can be used for checking
   * entity access *only* if the wrapper is not a property (i.e. has no parent
   * wrapper).
   * To be safe, better use EntityDrupalWrapper::entityAccess() for checking
   * entity access.
   */
  public function access($op, $account = NULL) {
    if (!empty($this->info['parent'])) {
      // If this is a property, make sure the user is able to view the
      // currently referenced entity also.
      if ($this->entityAccess('view', $account) === FALSE) {
        return FALSE;
      }
      if (parent::access($op, $account) === FALSE) {
        return FALSE;
      }
      // If access is unknown, we return TRUE.
      return TRUE;
    }
    else {
      // This is not a property, so fallback on entity access.
      if ($op == 'edit') {
        // If the operation is "edit" determine if its actually a "create" for
        // new un-saved entities, or an "update" for existing ones.
        return $this->entityAccess($this->getIdentifier() ? 'update' : 'create', $account);
      }
      return $this->entityAccess('view', $account);
    }
  }

  /**
   * Checks whether the operation $op is allowed on the entity.
   *
   * @see entity_access()
   */
  public function entityAccess($op, $account = NULL) {
    $entity = $this->dataAvailable() ? $this->value() : NULL;
    // The value() method could return FALSE on entities such as user 0, so we
    // need to use NULL instead to conform to the expectations of
    // entity_access().
    if ($entity === FALSE) {
      $entity = NULL;
    }
    return entity_access($op, $this->type, $entity, $account);
  }

  /**
   * Permanently save the wrapped entity.
   *
   * @throws EntityMetadataWrapperException
   *   If the entity type does not support saving.
   *
   * @return EntityDrupalWrapper
   */
  public function save() {
    if ($this->data) {
      if (!entity_type_supports($this->type, 'save')) {
        throw new EntityMetadataWrapperException("There is no information about how to save entities of type " . check_plain($this->type) . '.');
      }
      entity_save($this->type, $this->data);
      // On insert, update the identifier afterwards.
      if (!$this->id) {
        list($this->id, , ) = entity_extract_ids($this->type, $this->data);
      }
    }
    // If the entity hasn't been loaded yet, don't bother saving it.
    return $this;
  }

  /**
   * Permanently delete the wrapped entity.
   *
   * @return EntityDrupalWrapper
   */
  public function delete() {
    if ($this->dataAvailable() && $this->value()) {
      $return = entity_delete($this->type, $this->id);
      if ($return === FALSE) {
        throw new EntityMetadataWrapperException("There is no information about how to delete entities of type " . check_plain($this->type) . '.');
      }
    }
    return $this;
  }

  /**
   * Gets the info about the wrapped entity.
   */
  public function entityInfo() {
    return $this->entityInfo;
  }

  /**
   * Returns the name of the key used by the entity for given entity key.
   *
   * @param $name
   *   One of 'id', 'name', 'bundle' or 'revision'.
   * @return
   *   The name of the key used by the entity.
   */
  public function entityKey($name) {
    return isset($this->entityInfo['entity keys'][$name]) ? $this->entityInfo['entity keys'][$name] : FALSE;
  }

  /**
   * Returns the entity label.
   *
   * @see entity_label()
   */
  public function label() {
    if ($entity = $this->value()) {
      return entity_label($this->type, $entity);
    }
  }

  /**
   * Returns a string to use to identify this wrapper in error messages.
   */
  public function debugIdentifierLocation() {
    // An entity wrapper can be at the top of the chain or a part of it.
    if (isset($this->info['name'])) {
      // This wrapper is part of a chain, eg in the position node->author.
      // Return the name.
      $debug = $this->info['name'];
    }
    else {
      // This is a wrapper for an actual entity: return its type and id.
      $debug = $this->info['type'] . '(' . $this->getIdentifier() . ')';
    }

    if (isset($this->info['parent'])) {
      $debug = $this->info['parent']->debugIdentifierLocation() . '->' . $debug;
    }
    return $debug;
  }

  /**
   * Prepare for serializiation.
   */
  public function __sleep() {
    $vars = parent::__sleep();
    // Don't serialize the loaded entity and its property info.
    unset($vars['data'], $vars['propertyInfo'], $vars['propertyInfoAltered'], $vars['entityInfo']);
    // In case the entity is not saved yet, serialize the unsaved data.
    if ($this->dataAvailable() && $this->id === FALSE) {
      $vars['data'] = 'data';
    }
    return $vars;
  }

  public function __wakeup() {
    $this->setUp();
    if ($this->id !== FALSE) {
      // Make sure data is set, so the entity will be loaded when needed.
      $this->data = FALSE;
    }
  }
}

/**
 * Wraps a list of values.
 *
 * If the wrapped data is a list of data, its numerical indexes may be used to
 * retrieve wrappers for the list items. For that this wrapper implements
 * ArrayAccess so it may be used like a usual numerically indexed array.
 */
class EntityListWrapper extends EntityMetadataWrapper implements IteratorAggregate, ArrayAccess, Countable {

  /**
   * The type of contained items.
   */
  protected $itemType;

  /**
   * Whether this is a list of entities with a known entity type, i.e. for
   * generic list of entities (list<entity>) this is FALSE.
   */
  protected $isEntityList;


  public function __construct($type, $data = NULL, $info = array()) {
    parent::__construct($type, NULL, $info);

    $this->itemType = entity_property_list_extract_type($this->type);
    if (!$this->itemType) {
      $this->itemType = 'unknown';
    }
    $this->isEntityList = (bool) entity_get_info($this->itemType);

    if (isset($data)) {
      $this->set($data);
    }
  }

  /**
   * Get the wrapper for a single item.
   *
   * @return
   *   An instance of EntityMetadataWrapper.
   */
  public function get($delta) {
    // Look it up in the cache if possible.
    if (!array_key_exists($delta, $this->cache)) {
      if (!isset($delta)) {
        // The [] operator has been used so point at a new entry.
        $values = parent::value();
        $delta = $values ? max(array_keys($values)) + 1 : 0;
      }
      if (is_numeric($delta)) {
        $info = array('parent' => $this, 'name' => $delta) + $this->info;
        $this->cache[$delta] = entity_metadata_wrapper($this->itemType, NULL, $info);
      }
      else {
        throw new EntityMetadataWrapperException('There can be only numerical keyed items in a list.');
      }
    }
    return $this->cache[$delta];
  }

  protected function getPropertyValue($delta) {
    // Make use parent::value() to easily by-pass any entity-loading.
    $data = parent::value();
    if (isset($data[$delta])) {
      return $data[$delta];
    }
  }

  protected function getPropertyRaw($delta) {
    return $this->getPropertyValue($delta);
  }

  protected function setProperty($delta, $value) {
    $data = parent::value();
    if (is_numeric($delta)) {
      $data[$delta] = $value;
      $this->set($data);
    }
  }

  protected function propertyAccess($delta, $op, $account = NULL) {
    return $this->access($op, $account);
  }

  /**
   * Returns the list as numerically indexed array.
   *
   * Note that a list of entities might contain stale entity references. In
   * that case the wrapper and the identifier of a stale reference would be
   * still accessible, however the entity object value would be NULL. That way,
   * there may be NULL values in lists of entity objects due to stale entity
   * references.
   *
   * @param $options
   *   An array of options. Known keys:
   *   - identifier: If set to TRUE for a list of entities, it won't be returned
   *     as list of fully loaded entity objects, but as a list of entity ids.
   *     Note that this list may contain ids of stale entity references.
   */
  public function value(array $options = array()) {
    // For lists of entities fetch full entity objects before returning.
    // Generic entity-wrappers need to be handled separately though.
    if ($this->isEntityList && empty($options['identifier']) && $this->dataAvailable()) {
      $list = parent::value();
      $entities = $list ? entity_load($this->get(0)->type, $list) : array();
      // Make sure to keep the array keys as present in the list.
      foreach ($list as $key => $id) {
        // In case the entity cannot be loaded, we return NULL just as for empty
        // properties.
        $list[$key] = isset($entities[$id]) ? $entities[$id] : NULL;
      }
      return $list;
    }
    return parent::value();
  }

  public function set($values) {
    // Support setting lists of fully loaded entities.
    if ($this->isEntityList && $values && is_object(reset($values))) {
      foreach ($values as $key => $value) {
        // Ignore outdated NULL value references in lists of entities.
        if (isset($value)) {
          list($id, $vid, $bundle) = entity_extract_ids($this->itemType, $value);
          $values[$key] = $id;
        }
      }
    }
    return parent::set($values);
  }

  /**
   * If we wrap a list, we return an iterator over the data list.
   */
  public function getIterator() {
    // In case there is no data available, just iterate over the first item.
    return new EntityMetadataWrapperIterator($this, ($this->dataAvailable() && is_array(parent::value())) ? array_keys(parent::value()) : array(0));
  }

  /**
   * Implements the ArrayAccess interface.
   */
  public function offsetGet($delta) {
    return $this->get($delta);
  }

  public function offsetExists($delta) {
    return $this->dataAvailable() && ($data = $this->value()) && array_key_exists($delta, $data);
  }

  public function offsetSet($delta, $value) {
    $this->get($delta)->set($value);
  }

  public function offsetUnset($delta) {
    if ($this->offsetExists($delta)) {
      unset($this->data[$delta]);
      $this->set($this->data);
    }
  }

  public function count() {
    return $this->dataAvailable() ? count($this->value()) : 0;
  }

  /**
   * Overridden.
   */
  public function validate($value) {
    // Required lists may not be empty or unset.
    if (!empty($this->info['required']) && empty($value)) {
      return FALSE;
    }
    return parent::validate($value);
  }

  /**
   * Returns the label for the list of set values if available.
   */
  public function label() {
    if ($options = $this->optionsList('view')) {
      $options = entity_property_options_flatten($options);
      $labels = array_intersect_key($options, array_flip((array) parent::value()));
    }
    else {
      // Get each label on its own, e.g. to support getting labels of a list
      // of entities.
      $labels = array();
      foreach ($this as $key => $property) {
        $label = $property->label();
        if (!$label) {
          return NULL;
        }
        $labels[] = $label;
      }
    }
    return isset($labels) ? implode(', ', $labels) : NULL;
  }
}

/**
 * Provide a separate Exception so it can be caught separately.
 */
class EntityMetadataWrapperException extends Exception { }


/**
 * Allows to easily iterate over existing child wrappers.
 */
class EntityMetadataWrapperIterator implements RecursiveIterator {

  protected $position = 0;
  protected $wrapper, $keys;

  public function __construct(EntityMetadataWrapper $wrapper, array $keys) {
    $this->wrapper = $wrapper;
    $this->keys = $keys;
  }

  function rewind() {
    $this->position = 0;
  }

  function current() {
    return $this->wrapper->get($this->keys[$this->position]);
  }

  function key() {
    return $this->keys[$this->position];
  }

  function next() {
    $this->position++;
  }

  function valid() {
    return isset($this->keys[$this->position]);
  }

  public function hasChildren() {
    return $this->current() instanceof IteratorAggregate;
  }

  public function getChildren() {
    return $this->current()->getIterator();
  }
}

/**
 * An array object implementation keeping the reference on the given array so
 * changes to the object are reflected in the passed array.
 */
class EntityMetadataArrayObject implements ArrayAccess, Countable, IteratorAggregate {

  protected $data;

  public function __construct(&$array) {
    $this->data =& $array;
  }

  public function &getArray() {
    return $this->data;
  }

  /**
   * Implements the ArrayAccess interface.
   */
  public function offsetGet($delta) {
    return $this->data[$delta];
  }

  public function offsetExists($delta) {
    return array_key_exists($delta, $this->data);
  }

  public function offsetSet($delta, $value) {
    $this->data[$delta] = $value;
  }

  public function offsetUnset($delta) {
    unset($this->data[$delta]);
  }

  public function count() {
    return count($this->data);
  }

  public function getIterator() {
    return new ArrayIterator($this->data);
  }
}

?>