node.module

<?php
// $Id$

/**
 * @file
 * The core that allows content to be submitted to the site. Modules and
 * scripts may programmatically submit nodes using the usual form API pattern.
 */

/**
 * Nodes changed before this time are always marked as read.
 *
 * Nodes changed after this time may be marked new, updated, or read, depending
 * on their state for the current user. Defaults to 30 days ago.
 */
define('NODE_NEW_LIMIT', REQUEST_TIME - 30 * 24 * 60 * 60);

/**
 * Node is being built before being viewed normally.
 */
define('NODE_BUILD_NORMAL', 0);

/**
 * Node is being built before being previewed.
 */
define('NODE_BUILD_PREVIEW', 1);

/**
 * Node is being built before being indexed by search module.
 */
define('NODE_BUILD_SEARCH_INDEX', 2);

/**
 * Node is being built before being displayed as a search result.
 */
define('NODE_BUILD_SEARCH_RESULT', 3);

/**
 * Node is being built before being displayed as part of an RSS feed.
 */
define('NODE_BUILD_RSS', 4);

/**
 * Node is being built before being printed.
 */
define('NODE_BUILD_PRINT', 5);

/**
 * Implementation of hook_help().
 */
function node_help($path, $arg) {
  // Remind site administrators about the {node_access} table being flagged
  // for rebuild. We don't need to issue the message on the confirm form, or
  // while the rebuild is being processed.
  if ($path != 'admin/content/node-settings/rebuild' && $path != 'batch' && strpos($path, '#') === FALSE
      && user_access('access administration pages') && node_access_needs_rebuild()) {
    if ($path == 'admin/content/node-settings') {
      $message = t('The content access permissions need to be rebuilt.');
    }
    else {
      $message = t('The content access permissions need to be rebuilt. Please visit <a href="@node_access_rebuild">this page</a>.', array('@node_access_rebuild' => url('admin/content/node-settings/rebuild')));
    }
    drupal_set_message($message, 'error');
  }

  switch ($path) {
    case 'admin/help#node':
      $output = '<p>' . t('The node module manages content on your site, and stores all posts (regardless of type) as a "node" . In addition to basic publishing settings, including whether the post has been published, promoted to the site front page, or should remain present (or sticky) at the top of lists, the node module also records basic information about the author of a post. Optional revision control over edits is available. For additional functionality, the node module is often extended by other modules.') . '</p>';
      $output .= '<p>' . t('Though each post on your site is a node, each post is also of a particular <a href="@content-type">content type</a>. <a href="@content-type">Content types</a> are used to define the characteristics of a post, including the title and description of the fields displayed on its add and edit pages. Each content type may have different default settings for <em>Publishing options</em> and other workflow controls. By default, the two content types in a standard Drupal installation are <em>Page</em> and <em>Story</em>. Use the <a href="@content-type">content types page</a> to add new or edit existing content types. Additional content types also become available as you enable additional core, contributed and custom modules.', array('@content-type' => url('admin/build/types'))) . '</p>';
      $output .= '<p>' . t('The administrative <a href="@content">content page</a> allows you to review and manage your site content. The <a href="@post-settings">post settings page</a> sets certain options for the display of posts. The node module makes a number of permissions available for each content type, which may be set by role on the <a href="@permissions">permissions page</a>.', array('@content' => url('admin/content/node'), '@post-settings' => url('admin/content/node-settings'), '@permissions' => url('admin/user/permissions'))) . '</p>';
      $output .= '<p>' . t('For more information, see the online handbook entry for <a href="@node">Node module</a>.', array('@node' => 'http://drupal.org/handbook/modules/node/')) . '</p>';
      return $output;
    case 'admin/content/node':
      return ' '; // Return a non-null value so that the 'more help' link is shown.
    case 'admin/build/types':
      return '<p>' . t('Below is a list of all the content types on your site. All posts that exist on your site are instances of one of these content types.') . '</p>';
    case 'admin/build/types/add':
      return '<p>' . t('To create a new content type, enter the human-readable name, the machine-readable name, and all other relevant fields that are on this page. Once created, users of your site will be able to create posts that are instances of this content type.') . '</p>';
    case 'node/%/revisions':
      return '<p>' . t('The revisions let you track differences between multiple versions of a post.') . '</p>';
    case 'node/%/edit':
      $node = node_load($arg[1]);
      $type = node_get_types('type', $node->type);
      return (!empty($type->help) ? '<p>' . filter_xss_admin($type->help) . '</p>' : '');
  }

  if ($arg[0] == 'node' && $arg[1] == 'add' && $arg[2]) {
    $type = node_get_types('type', str_replace('-', '_', $arg[2]));
    return (!empty($type->help) ? '<p>' . filter_xss_admin($type->help) . '</p>' : '');
  }
}

/**
 * Implementation of hook_theme().
 */
function node_theme() {
  return array(
    'node' => array(
      'arguments' => array('elements' => NULL),
      'template' => 'node',
    ),
    'node_list' => array(
      'arguments' => array('items' => NULL, 'title' => NULL),
    ),
    'node_search_admin' => array(
      'arguments' => array('form' => NULL),
    ),
    'node_filter_form' => array(
      'arguments' => array('form' => NULL),
      'file' => 'node.admin.inc',
    ),
    'node_filters' => array(
      'arguments' => array('form' => NULL),
      'file' => 'node.admin.inc',
    ),
    'node_admin_nodes' => array(
      'arguments' => array('form' => NULL),
      'file' => 'node.admin.inc',
    ),
    'node_add_list' => array(
      'arguments' => array('content' => NULL),
      'file' => 'node.pages.inc',
    ),
    'node_form' => array(
      'arguments' => array('form' => NULL),
      'file' => 'node.pages.inc',
    ),
    'node_preview' => array(
      'arguments' => array('node' => NULL),
      'file' => 'node.pages.inc',
    ),
    'node_log_message' => array(
      'arguments' => array('log' => NULL),
    ),
    'node_submitted' => array(
      'arguments' => array('node' => NULL),
    ),
    'node_admin_overview' => array(
      'arguments' => array('name' => NULL, 'type' => NULL),
    ),
    'node_links' => array(
      'arguments' => array('element' => NULL),
    ),
  );
}

/**
 * Implementation of hook_cron().
 */
function node_cron() {
  db_query('DELETE FROM {history} WHERE timestamp < %d', NODE_NEW_LIMIT);
}

/**
 * Implementation of hook_fieldable_info().
 */
function node_fieldable_info() {
  $return = array(
    'node' => array(
      'name' => t('Node'),
      'id key' => 'nid',
      'revision key' => 'vid',
      'bundle key' => 'type',
      // Node.module handles its own caching.
      // 'cacheable' => FALSE,
      // Bundles must provide human readable name so
      // we can create help and error messages about them.
      'bundles' => node_get_types('names'),
    ),
  );
  return $return;
}


/**
 * Implementation of hook_field_build_modes().
 */
function node_field_build_modes($obj_type) {
  $modes = array();
  if ($obj_type == 'node') {
    $modes = array(
      'teaser' => t('Teaser'),
      'full' => t('Full node'),
      NODE_BUILD_RSS => t('RSS'),
      NODE_BUILD_PRINT => t('Print'),
    );
    if (module_exists('search')) {
      $modes += array(
        NODE_BUILD_SEARCH_INDEX => t('Search Index'),
        NODE_BUILD_SEARCH_RESULT => t('Search Result'),
      );
    }
  }
  return $modes;
}

/**
 * Gather a listing of links to nodes.
 *
 * @param $result
 *   A DB result object from a query to fetch node objects. If your query
 *   joins the <code>node_comment_statistics</code> table so that the
 *   <code>comment_count</code> field is available, a title attribute will
 *   be added to show the number of comments.
 * @param $title
 *   A heading for the resulting list.
 *
 * @return
 *   An HTML list suitable as content for a block, or FALSE if no result can
 *   fetch from DB result object.
 */
function node_title_list($result, $title = NULL) {
  $items = array();
  $num_rows = FALSE;
  while ($node = db_fetch_object($result)) {
    $items[] = l($node->title, 'node/' . $node->nid, !empty($node->comment_count) ? array('attributes' => array('title' => format_plural($node->comment_count, '1 comment', '@count comments'))) : array());
    $num_rows = TRUE;
  }

  return $num_rows ? theme('node_list', $items, $title) : FALSE;
}

/**
 * Format a listing of links to nodes.
 *
 * @ingroup themeable
 */
function theme_node_list($items, $title = NULL) {
  return theme('item_list', $items, $title);
}

/**
 * Update the 'last viewed' timestamp of the specified node for current user.
 */
function node_tag_new($nid) {
  global $user;

  if ($user->uid) {
    if (node_last_viewed($nid)) {
      db_query('UPDATE {history} SET timestamp = %d WHERE uid = %d AND nid = %d', REQUEST_TIME, $user->uid, $nid);
    }
    else {
      @db_query('INSERT INTO {history} (uid, nid, timestamp) VALUES (%d, %d, %d)', $user->uid, $nid, REQUEST_TIME);
    }
  }
}

/**
 * Retrieves the timestamp at which the current user last viewed the
 * specified node.
 */
function node_last_viewed($nid) {
  global $user;
  static $history;

  if (!isset($history[$nid])) {
    $history[$nid] = db_fetch_object(db_query("SELECT timestamp FROM {history} WHERE uid = %d AND nid = %d", $user->uid, $nid));
  }

  return (isset($history[$nid]->timestamp) ? $history[$nid]->timestamp : 0);
}

/**
 * Decide on the type of marker to be displayed for a given node.
 *
 * @param $nid
 *   Node ID whose history supplies the "last viewed" timestamp.
 * @param $timestamp
 *   Time which is compared against node's "last viewed" timestamp.
 * @return
 *   One of the MARK constants.
 */
function node_mark($nid, $timestamp) {
  global $user;
  static $cache;

  if (!$user->uid) {
    return MARK_READ;
  }
  if (!isset($cache[$nid])) {
    $cache[$nid] = node_last_viewed($nid);
  }
  if ($cache[$nid] == 0 && $timestamp > NODE_NEW_LIMIT) {
    return MARK_NEW;
  }
  elseif ($timestamp > $cache[$nid] && $timestamp > NODE_NEW_LIMIT) {
    return MARK_UPDATED;
  }
  return MARK_READ;
}

/**
 * See if the user used JS to submit a teaser.
 */
function node_teaser_js(&$form, &$form_state) {
  if (isset($form['#post']['teaser_js'])) {
    // Glue the teaser to the body.
    if (trim($form_state['values']['teaser_js'])) {
      // Space the teaser from the body
      $body = trim($form_state['values']['teaser_js']) . "\r\n<!--break-->\r\n" . trim($form_state['values']['body']);
    }
    else {
      // Empty teaser, no spaces.
      $body = '<!--break-->' . $form_state['values']['body'];
    }
    // Pass updated body value on to preview/submit form processing.
    form_set_value($form['body'], $body, $form_state);
    // Pass updated body value back onto form for those cases
    // in which the form is redisplayed.
    $form['body']['#value'] = $body;
  }
  return $form;
}

/**
 * Ensure value of "teaser_include" checkbox is consistent with other form data.
 *
 * This handles two situations in which an unchecked checkbox is rejected:
 *
 *   1. The user defines a teaser (summary) but it is empty;
 *   2. The user does not define a teaser (summary) (in this case an
 *      unchecked checkbox would cause the body to be empty, or missing
 *      the auto-generated teaser).
 *
 * If JavaScript is active then it is used to force the checkbox to be
 * checked when hidden, and so the second case will not arise.
 *
 * In either case a warning message is output.
 */
function node_teaser_include_verify(&$form, &$form_state) {
  $message = '';

  // $form['#post'] is set only when the form is built for preview/submit.
  if (isset($form['#post']['body']) && isset($form_state['values']['teaser_include']) && !$form_state['values']['teaser_include']) {
    // "teaser_include" checkbox is present and unchecked.
    if (strpos($form_state['values']['body'], '<!--break-->') === 0) {
      // Teaser is empty string.
      $message = t('You specified that the summary should not be shown when this post is displayed in full view. This setting is ignored when the summary is empty.');
    }
    elseif (strpos($form_state['values']['body'], '<!--break-->') === FALSE) {
      // Teaser delimiter is not present in the body.
      $message = t('You specified that the summary should not be shown when this post is displayed in full view. This setting has been ignored since you have not defined a summary for the post. (To define a summary, insert the delimiter "&lt;!--break--&gt;" (without the quotes) in the Body of the post to indicate the end of the summary and the start of the main content.)');
    }

    if (!empty($message)) {
      drupal_set_message($message, 'warning');
      // Pass new checkbox value on to preview/submit form processing.
      form_set_value($form['teaser_include'], 1, $form_state);
      // Pass new checkbox value back onto form for those cases
      // in which form is redisplayed.
      $form['teaser_include']['#value'] = 1;
    }
  }

  return $form;
}

/**
 * Generate a teaser for a node body.
 *
 * If the end of the teaser is not indicated using the <!--break--> delimiter
 * then we generate the teaser automatically, trying to end it at a sensible
 * place such as the end of a paragraph, a line break, or the end of a
 * sentence (in that order of preference).
 *
 * @param $body
 *   The content for which a teaser will be generated.
 * @param $format
 *   The format of the content. If the content contains PHP code, we do not
 *   split it up to prevent parse errors. If the line break filter is present
 *   then we treat newlines embedded in $body as line breaks.
 * @param $size
 *   The desired character length of the teaser. If omitted, the default
 *   value will be used. Ignored if the special delimiter is present
 *   in $body.
 * @return
 *   The generated teaser.
 */
function node_teaser($body, $format = NULL, $size = NULL) {

  if (!isset($size)) {
    $size = variable_get('teaser_length', 600);
  }

  // Find where the delimiter is in the body
  $delimiter = strpos($body, '<!--break-->');

  // If the size is zero, and there is no delimiter, the entire body is the teaser.
  if ($size == 0 && $delimiter === FALSE) {
    return $body;
  }

  // If a valid delimiter has been specified, use it to chop off the teaser.
  if ($delimiter !== FALSE) {
    return substr($body, 0, $delimiter);
  }

  // We check for the presence of the PHP evaluator filter in the current
  // format. If the body contains PHP code, we do not split it up to prevent
  // parse errors.
  if (isset($format)) {
    $filters = filter_list_format($format);
    if (isset($filters['php/0']) && strpos($body, '<?') !== FALSE) {
      return $body;
    }
  }

  // If we have a short body, the entire body is the teaser.
  if (drupal_strlen($body) <= $size) {
    return $body;
  }

  // If the delimiter has not been specified, try to split at paragraph or
  // sentence boundaries.

  // The teaser may not be longer than maximum length specified. Initial slice.
  $teaser = truncate_utf8($body, $size);

  // Store the actual length of the UTF8 string -- which might not be the same
  // as $size.
  $max_rpos = strlen($teaser);

  // How much to cut off the end of the teaser so that it doesn't end in the
  // middle of a paragraph, sentence, or word.
  // Initialize it to maximum in order to find the minimum.
  $min_rpos = $max_rpos;

  // Store the reverse of the teaser. We use strpos on the reversed needle and
  // haystack for speed and convenience.
  $reversed = strrev($teaser);

  // Build an array of arrays of break points grouped by preference.
  $break_points = array();

  // A paragraph near the end of sliced teaser is most preferable.
  $break_points[] = array('</p>' => 0);

  // If no complete paragraph then treat line breaks as paragraphs.
  $line_breaks = array('<br />' => 6, '<br>' => 4);
  // Newline only indicates a line break if line break converter
  // filter is present.
  if (isset($filters['filter/1'])) {
    $line_breaks["\n"] = 1;
  }
  $break_points[] = $line_breaks;

  // If the first paragraph is too long, split at the end of a sentence.
  $break_points[] = array('. ' => 1, '! ' => 1, '? ' => 1, '。' => 0, '؟ ' => 1);

  // Iterate over the groups of break points until a break point is found.
  foreach ($break_points as $points) {
    // Look for each break point, starting at the end of the teaser.
    foreach ($points as $point => $offset) {
      // The teaser is already reversed, but the break point isn't.
      $rpos = strpos($reversed, strrev($point));
      if ($rpos !== FALSE) {
        $min_rpos = min($rpos + $offset, $min_rpos);
      }
    }

    // If a break point was found in this group, slice and return the teaser.
    if ($min_rpos !== $max_rpos) {
      // Don't slice with length 0. Length must be <0 to slice from RHS.
      return ($min_rpos === 0) ? $teaser : substr($teaser, 0, 0 - $min_rpos);
    }
  }

  // If a break point was not found, still return a teaser.
  return $teaser;
}

/**
 * Builds a list of available node types, and returns all of part of this list
 * in the specified format.
 *
 * @param $op
 *   The format in which to return the list. When this is set to 'type',
 *   'base', or 'name', only the specified node type is returned. When set to
 *   'types' or 'names', all node types are returned.
 * @param $node
 *   A node object, array, or string that indicates the node type to return.
 *   Leave at default value (NULL) to return a list of all node types.
 * @param $reset
 *   Whether or not to reset this function's internal cache (defaults to
 *   FALSE).
 *
 * @return
 *   Either an array of all available node types, or a single node type, in a
 *   variable format. Returns FALSE if the node type is not found.
 */
function node_get_types($op = 'types', $node = NULL, $reset = FALSE) {
  static $_node_types, $_node_names;

  if ($reset || !isset($_node_types)) {
    list($_node_types, $_node_names) = _node_types_build();
  }

  if ($node) {
    if (is_array($node)) {
      $type = $node['type'];
    }
    elseif (is_object($node)) {
      $type = $node->type;
    }
    elseif (is_string($node)) {
      $type = $node;
    }
    if (!isset($_node_types[$type])) {
      return FALSE;
    }
  }
  switch ($op) {
    case 'types':
      return $_node_types;
    case 'type':
      return isset($_node_types[$type]) ? $_node_types[$type] : FALSE;
    case 'base':
      return isset($_node_types[$type]->base) ? $_node_types[$type]->base : FALSE;
    case 'names':
      return $_node_names;
    case 'name':
      return isset($_node_names[$type]) ? $_node_names[$type] : FALSE;
  }
}

/**
 * Resets the database cache of node types, and saves all new or non-modified
 * module-defined node types to the database.
 */
function node_types_rebuild() {
  _node_types_build();

  $node_types = node_get_types('types', NULL, TRUE);

  foreach ($node_types as $type => $info) {
    if (!empty($info->is_new)) {
      node_type_save($info);
    }
    if (!empty($info->disabled)) {
      node_type_delete($info->type);
    }
  }

  _node_types_build();
  // This is required for proper menu items at node/add/type.
  menu_rebuild();
}

/**
 * Saves a node type to the database.
 *
 * @param $info
 *   The node type to save, as an object.
 *
 * @return
 *   Status flag indicating outcome of the operation.
 */
function node_type_save($info) {
  $is_existing = FALSE;
  $existing_type = !empty($info->old_type) ? $info->old_type : $info->type;
  $is_existing = db_result(db_query("SELECT COUNT(*) FROM {node_type} WHERE type = '%s'", $existing_type));
  $type = node_type_set_defaults($info);

  $fields = array(
    'type' => (string) $type->type,
    'name' => (string) $type->name,
    'base' => (string) $type->base,
    'has_title' => (int) $type->has_title,
    'title_label' => (string) $type->title_label,
    'has_body' => (int) $type->has_body,
    'body_label' => (string) $type->body_label,
    'description' => (string) $type->description,
    'help' => (string) $type->help,
    'min_word_count' => (int) $type->min_word_count,
    'custom' => (int) $type->custom,
    'modified' => (int) $type->modified,
    'locked' => (int) $type->locked,
  );

  if ($is_existing) {
    db_update('node_type')->fields($fields)->condition('type', $existing_type)->execute();

    if (!empty($type->old_type) && $type->old_type != $type->type) {
      field_attach_rename_bundle($type->old_type, $type->type);
    }
    module_invoke_all('node_type', 'update', $type);
    return SAVED_UPDATED;
  }
  else {
    $fields['orig_type'] = (string) $type->orig_type;
    db_insert('node_type')->fields($fields)->execute();

    field_attach_create_bundle($type->type);

    module_invoke_all('node_type', 'insert', $type);
    return SAVED_NEW;
  }
}

/**
 * Deletes a node type from the database.
 *
 * @param $type
 *   The machine-readable name of the node type to be deleted.
 */
function node_type_delete($type) {
  $info = node_get_types('type', $type);
  db_query("DELETE FROM {node_type} WHERE type = '%s'", $type);
  module_invoke_all('node_type', 'delete', $info);
}

/**
 * Updates all nodes of one type to be of another type.
 *
 * @param $old_type
 *   The current node type of the nodes.
 * @param $type
 *   The new node type of the nodes.
 *
 * @return
 *   The number of nodes whose node type field was modified.
 */
function node_type_update_nodes($old_type, $type) {
  db_query("UPDATE {node} SET type = '%s' WHERE type = '%s'", $type, $old_type);
  return db_affected_rows();
}

/**
 * Builds and returns the list of available node types.
 *
 * The list of types is built by querying hook_node_info() in all modules, and
 * by comparing this information with the node types in the {node_type} table.
 *
 */
function _node_types_build() {
  $_node_types = array();
  $_node_names = array();

  $info_array = module_invoke_all('node_info');
  foreach ($info_array as $type => $info) {
    $info['type'] = $type;
    $_node_types[$type] = node_type_set_defaults($info);
    $_node_names[$type] = $info['name'];
  }

  $type_result = db_query(db_rewrite_sql('SELECT nt.type, nt.* FROM {node_type} nt ORDER BY nt.type ASC', 'nt', 'type'));
  while ($type_object = db_fetch_object($type_result)) {
    // Check for node types from disabled modules and mark their types for removal.
    // Types defined by the node module in the database (rather than by a separate
    // module using hook_node_info) have a base value of 'node_content'. The isset()
    // check prevents errors on old (pre-Drupal 7) databases.
    if (isset($type_object->base) && $type_object->base != 'node_content' && empty($info_array[$type_object->type])) {
      $type_object->disabled = TRUE;
    }
    if (!isset($_node_types[$type_object->type]) || $type_object->modified) {
      $_node_types[$type_object->type] = $type_object;
      $_node_names[$type_object->type] = $type_object->name;

      if ($type_object->type != $type_object->orig_type) {
        unset($_node_types[$type_object->orig_type]);
        unset($_node_names[$type_object->orig_type]);
      }
    }
  }

  asort($_node_names);

  return array($_node_types, $_node_names);
}

/**
 * Set the default values for a node type.
 *
 * The defaults are for a type defined through hook_node_info().
 * When populating a custom node type $info should have the 'custom'
 * key set to 1.
 *
 * @param $info
 *   An object or array containing values to override the defaults.
 *
 * @return
 *  A node type object.
 */
function node_type_set_defaults($info = array()) {
  static $type;

  if (!isset($type)) {
    $type = new stdClass();
    $type->type = '';
    $type->name = '';
    $type->base = '';
    $type->description = '';
    $type->help = '';
    $type->min_word_count = 0;
    $type->has_title = 1;
    $type->has_body = 1;
    $type->title_label = t('Title');
    $type->body_label = t('Body');
    $type->custom = 0;
    $type->modified = 0;
    $type->locked = 1;
    $type->is_new = 1;
  }

  $new_type = clone $type;
  $info = (array) $info;
  foreach ($info as $key => $data) {
    $new_type->$key = $data;
  }
  // If the type has no title or body, set an empty label.
  if (!$new_type->has_title) {
    $new_type->title_label = '';
  }
  if (!$new_type->has_body) {
    $new_type->body_label = '';
  }
  $new_type->orig_type = isset($info['type']) ? $info['type'] : '';

  return $new_type;
}

/**
 * Determine whether a node hook exists.
 *
 * @param &$node
 *   Either a node object, node array, or a string containing the node type.
 * @param $hook
 *   A string containing the name of the hook.
 * @return
 *   TRUE iff the $hook exists in the node type of $node.
 */
function node_hook(&$node, $hook) {
  $base = node_get_types('base', $node);
  return module_hook($base, $hook);
}

/**
 * Invoke a node hook.
 *
 * @param &$node
 *   Either a node object, node array, or a string containing the node type.
 * @param $hook
 *   A string containing the name of the hook.
 * @param $a2, $a3, $a4
 *   Arguments to pass on to the hook, after the $node argument.
 * @return
 *   The returned value of the invoked hook.
 */
function node_invoke(&$node, $hook, $a2 = NULL, $a3 = NULL, $a4 = NULL) {
  if (node_hook($node, $hook)) {
    $base = node_get_types('base', $node);
    $function = $base . '_' . $hook;
    return ($function($node, $a2, $a3, $a4));
  }
}

/**
 * Invoke a hook_nodeapi() operation in all modules.
 *
 * @param &$node
 *   A node object.
 * @param $op
 *   A string containing the name of the nodeapi operation.
 * @param $a3, $a4
 *   Arguments to pass on to the hook, after the $node and $op arguments.
 * @return
 *   The returned value of the invoked hooks.
 */
function node_invoke_nodeapi(&$node, $op, $a3 = NULL, $a4 = NULL) {
  $return = array();
  $hook = 'nodeapi_' . $op;
  foreach (module_implements($hook) as $module) {
    $function = $module . '_' . $hook;
    $result = $function($node, $a3, $a4);
    if (isset($result) && is_array($result)) {
      $return = array_merge($return, $result);
    }
    elseif (isset($result)) {
      $return[] = $result;
    }
  }
  return $return;
}

/**
 * Load node objects from the database.
 *
 * This function should be used whenever you need to load more than one node
 * from the database. Nodes are loaded into memory and will not require
 * database access if loaded again during the same page request.
 *
 * @param $nids
 *   An array of node IDs.
 * @param $conditions
 *   An array of conditions on the {node} table in the form 'field' => $value.
 * @param $reset
 *   Whether to reset the internal node_load cache.
 *
 * @return
 *   An array of node objects indexed by nid.
 */
function node_load_multiple($nids = array(), $conditions = array(), $reset = FALSE) {
  static $node_cache = array();
  if ($reset) {
    $node_cache = array();
  }
  $nodes = array();

  // Create a new variable which is either a prepared version of the $nids
  // array for later comparison with the node cache, or FALSE if no $nids were
  // passed. The $nids array is reduced as items are loaded from cache, and we
  // need to know if it's empty for this reason to avoid querying the database
  // when all requested nodes are loaded from cache.
  $passed_nids = !empty($nids) ? array_flip($nids) : FALSE;

  // Revisions are not statically cached, and require a different query to
  // other conditions, so separate vid into its own variable.
  $vid = isset($conditions['vid']) ? $conditions['vid'] : FALSE;
  unset($conditions['vid']);

  // Load any available nodes from the internal cache.
  if ($node_cache && !$vid) {
    if ($nids) {
      $nodes += array_intersect_key($node_cache, $passed_nids);
      // If any nodes were loaded, remove them from the $nids still to load.
      $nids = array_keys(array_diff_key($passed_nids, $nodes));
    }
    // If loading nodes only by conditions, fetch all available nodes from
    // the cache. Nodes which don't match are removed later.
    elseif ($conditions) {
      $nodes = $node_cache;
    }
  }

  // Exclude any nodes loaded from cache if they don't match $conditions.
  // This ensures the same behavior whether loading from memory or database.
  if ($conditions) {
    foreach ($nodes as $node) {
      $node_values = (array) $node;
      if (array_diff_assoc($conditions, $node_values)) {
        unset($nodes[$node->nid]);
      }
    }
  }

  // Load any remaining nodes from the database. This is the case if there are
  // any $nids left to load, if loading a revision, or if $conditions was
  // passed without $nids.
  if ($nids || $vid || ($conditions && !$passed_nids)) {
    $query = db_select('node', 'n');

    if ($vid) {
      $query->join('node_revision', 'r', 'r.nid = n.nid AND r.vid = :vid', array(':vid' => $vid));
    }
    else {
      $query->join('node_revision', 'r', 'r.vid = n.vid');
    }
    $query->join('users', 'u', 'u.uid = n.uid');

    // Add fields from the {node} table.
    $node_fields = drupal_schema_fields_sql('node');

    // vid and title are provided by node_revision, so remove them.
    unset($node_fields['vid']);
    unset($node_fields['title']);
    $query->fields('n', $node_fields);

    // Add all fields from the {node_revision} table.
    $node_revision_fields = drupal_schema_fields_sql('node_revision');

    // nid is provided by node, so remove it.
    unset($node_revision_fields['nid']);

    // Change timestamp to revision_timestamp before adding it to the query.
    unset($node_revision_fields['timestamp']);
    $query->addField('r', 'timestamp', 'revision_timestamp');
    $query->fields('r', $node_revision_fields);

    // Add fields from the {users} table.
    $user_fields = array('name', 'picture', 'data');
    $query->fields('u', $user_fields);

    if ($nids) {
      $query->condition('n.nid', $nids, 'IN');
    }
    if ($conditions) {
      foreach ($conditions as $field => $value) {
        $query->condition('n.' . $field, $value);
      }
    }
    $queried_nodes = $query->execute()->fetchAllAssoc('nid');
  }

  // Pass all nodes loaded from the database through the node type specific
  // callbacks and hook_nodeapi_load(), then add them to the internal cache.
  if (!empty($queried_nodes)) {
    // Create an array of nodes for each content type and pass this to the
    // node type specific callback.
    $typed_nodes = array();
    foreach ($queried_nodes as $nid => $node) {
      $typed_nodes[$node->type][$nid] = $node;
    }

    // Call node type specific callbacks on each typed array of nodes.
    foreach ($typed_nodes as $type => $nodes_of_type) {
      if (node_hook($type, 'load')) {
        $function = node_get_types('base', $type) . '_load';
        $function($nodes_of_type);
      }
    }

    // Attach fields.
    if ($vid) {
      field_attach_load_revision('node', $queried_nodes);
    }
    else {
      field_attach_load('node', $queried_nodes);
    }

    // Call hook_nodeapi_load(), pass the node types so modules can return early
    // if not acting on types in the array.
    foreach (module_implements('nodeapi_load') as $module) {
      $function = $module . '_nodeapi_load';
      $function($queried_nodes, array_keys($typed_nodes));
    }
    $nodes += $queried_nodes;
    // Add nodes to the cache if we're not loading a revision.
    if (!$vid) {
      $node_cache += $queried_nodes;
    }
  }

  // Ensure that the returned array is ordered the same as the original $nids
  // array if this was passed in and remove any invalid nids.
  if ($passed_nids) {
    // Remove any invalid nids from the array.
    $passed_nids = array_intersect_key($passed_nids, $nodes);
    foreach ($nodes as $node) {
      $passed_nids[$node->nid] = $node;
    }
    $nodes = $passed_nids;
  }

  return $nodes;
}

/**
 * Load a node object from the database.
 *
 * @param $nid
 *   The node ID.
 * @param $vid
 *   The revision ID.
 * @param $reset
 *   Whether to reset the internal node_load cache.
 *
 * @return
 *   A fully-populated node object.
 */
function node_load($nid, $vid = array(), $reset = FALSE) {
  $vid = isset($vid) ? array('vid' => $vid) : NULL;
  $node = node_load_multiple(array($nid), $vid, $reset);

  return $node ? $node[$nid] : FALSE;
}

/**
 * Perform validation checks on the given node.
 */
function node_validate($node, $form = array()) {
  // Convert the node to an object, if necessary.
  $node = (object)$node;
  $type = node_get_types('type', $node);

  // Make sure the body has the minimum number of words.
  // TODO : use a better word counting algorithm that will work in other languages
  if (!empty($type->min_word_count) && isset($node->body) && count(explode(' ', $node->body)) < $type->min_word_count) {
    form_set_error('body', t('The body of your @type is too short. You need at least %words words.', array('%words' => $type->min_word_count, '@type' => $type->name)));
  }

  if (isset($node->nid) && (node_last_changed($node->nid) > $node->changed)) {
    form_set_error('changed', t('This content has been modified by another user, changes cannot be saved.'));
  }

  if (user_access('administer nodes')) {
    // Validate the "authored by" field.
    if (!empty($node->name) && !($account = user_load(array('name' => $node->name)))) {
      // The use of empty() is mandatory in the context of usernames
      // as the empty string denotes the anonymous user. In case we
      // are dealing with an anonymous user we set the user ID to 0.
      form_set_error('name', t('The username %name does not exist.', array('%name' => $node->name)));
    }

    // Validate the "authored on" field.
    if (!empty($node->date) && strtotime($node->date) === FALSE) {
      form_set_error('date', t('You have to specify a valid date.'));
    }
  }

  // Validate fields