search.module

  1. drupal
    1. 5
    2. 8
    3. 6
    4. 7

Enables site-wide keyword searching.

Functions & methods

NameDescription
do_searchDo a query on the full-text search index for a word or words.
search_blockImplementation of hook_block().
search_boxForm builder; Output a search form for the search block and the theme's search box.
search_box_form_submitProcess a block search form submission.
search_commentImplementation of hook_comment().
search_cronImplementation of hook_cron().
search_dataPerform a standard search on the given keys, and return the formatted results.
search_dirtyMarks a word as dirty (or retrieves the list of dirty words). This is used during indexing (cron). Words which are dirty have outdated total counts in the search_total table, and need to be recounted.
search_excerptReturns snippets from a piece of text, with certain keywords highlighted. Used for formatting search results.
search_expand_cjkBasic CJK tokenizer. Simply splits a string into consecutive, overlapping sequences of characters ('minimum_word_size' long).
search_formRender a search form.
search_forms
search_get_keysHelper function for grabbing search keys.
search_helpImplementation of hook_help().
search_indexUpdate the full-text search index for a particular item.
search_index_splitSplits a string into tokens for indexing.
search_invoke_preprocessInvokes hook_search_preprocess() in modules.
search_menuImplementation of hook_menu().
search_nodeapiImplementation of hook_nodeapi().
search_parse_queryParse a search query into SQL conditions.
search_permImplementation of hook_perm().
search_query_extractExtract a module-specific search option from a search query. e.g. 'type:book'
search_query_insertReturn a query with the given module-specific search option inserted in. e.g. 'type:book'.
search_simplifySimplifies a string according to indexing rules.
search_themeImplementation of hook_theme()
search_touch_nodeChange a node's changed timestamp to 'now' to force reindexing.
search_update_totalsThis function is called on shutdown to ensure that search_total is always up to date (even if cron times out or otherwise fails).
search_wipeWipes a part of or the entire search index.
template_preprocess_search_block_formProcess variables for search-block-form.tpl.php.
template_preprocess_search_theme_formProcess variables for search-theme-form.tpl.php.
_search_excerpt_replaceHelper function for array_walk in search_except.
_search_index_truncateHelper function for array_walk in search_index_split.
_search_menu
_search_parse_queryHelper function for search_parse_query();

Constants

NameDescription
PREG_CLASS_CJKMatches all CJK characters that are candidates for auto-splitting (Chinese, Japanese, Korean). Contains kana and BMP ideographs.
PREG_CLASS_NUMBERSMatches all 'N' Unicode character classes (numbers)
PREG_CLASS_PUNCTUATIONMatches all 'P' Unicode character classes (punctuation)
PREG_CLASS_SEARCH_EXCLUDEMatches Unicode character classes to exclude from the search index.
View source
<?php

/**
 * @file
 * Enables site-wide keyword searching.
 */

/**
 * Matches Unicode character classes to exclude from the search index.
 *
 * See: http://www.unicode.org/Public/UNIDATA/UCD.html#General_Category_Values
 *
 * The index only contains the following character classes:
 * Lu     Letter, Uppercase
 * Ll     Letter, Lowercase
 * Lt     Letter, Titlecase
 * Lo     Letter, Other
 * Nd     Number, Decimal Digit
 * No     Number, Other
 */
define('PREG_CLASS_SEARCH_EXCLUDE',
'\x{0}-\x{2f}\x{3a}-\x{40}\x{5b}-\x{60}\x{7b}-\x{bf}\x{d7}\x{f7}\x{2b0}-'.
'\x{385}\x{387}\x{3f6}\x{482}-\x{489}\x{559}-\x{55f}\x{589}-\x{5c7}\x{5f3}-'.
'\x{61f}\x{640}\x{64b}-\x{65e}\x{66a}-\x{66d}\x{670}\x{6d4}\x{6d6}-\x{6ed}'.
'\x{6fd}\x{6fe}\x{700}-\x{70f}\x{711}\x{730}-\x{74a}\x{7a6}-\x{7b0}\x{901}-'.
'\x{903}\x{93c}\x{93e}-\x{94d}\x{951}-\x{954}\x{962}-\x{965}\x{970}\x{981}-'.
'\x{983}\x{9bc}\x{9be}-\x{9cd}\x{9d7}\x{9e2}\x{9e3}\x{9f2}-\x{a03}\x{a3c}-'.
'\x{a4d}\x{a70}\x{a71}\x{a81}-\x{a83}\x{abc}\x{abe}-\x{acd}\x{ae2}\x{ae3}'.
'\x{af1}-\x{b03}\x{b3c}\x{b3e}-\x{b57}\x{b70}\x{b82}\x{bbe}-\x{bd7}\x{bf0}-'.
'\x{c03}\x{c3e}-\x{c56}\x{c82}\x{c83}\x{cbc}\x{cbe}-\x{cd6}\x{d02}\x{d03}'.
'\x{d3e}-\x{d57}\x{d82}\x{d83}\x{dca}-\x{df4}\x{e31}\x{e34}-\x{e3f}\x{e46}-'.
'\x{e4f}\x{e5a}\x{e5b}\x{eb1}\x{eb4}-\x{ebc}\x{ec6}-\x{ecd}\x{f01}-\x{f1f}'.
'\x{f2a}-\x{f3f}\x{f71}-\x{f87}\x{f90}-\x{fd1}\x{102c}-\x{1039}\x{104a}-'.
'\x{104f}\x{1056}-\x{1059}\x{10fb}\x{10fc}\x{135f}-\x{137c}\x{1390}-\x{1399}'.
'\x{166d}\x{166e}\x{1680}\x{169b}\x{169c}\x{16eb}-\x{16f0}\x{1712}-\x{1714}'.
'\x{1732}-\x{1736}\x{1752}\x{1753}\x{1772}\x{1773}\x{17b4}-\x{17db}\x{17dd}'.
'\x{17f0}-\x{180e}\x{1843}\x{18a9}\x{1920}-\x{1945}\x{19b0}-\x{19c0}\x{19c8}'.
'\x{19c9}\x{19de}-\x{19ff}\x{1a17}-\x{1a1f}\x{1d2c}-\x{1d61}\x{1d78}\x{1d9b}-'.
'\x{1dc3}\x{1fbd}\x{1fbf}-\x{1fc1}\x{1fcd}-\x{1fcf}\x{1fdd}-\x{1fdf}\x{1fed}-'.
'\x{1fef}\x{1ffd}-\x{2070}\x{2074}-\x{207e}\x{2080}-\x{2101}\x{2103}-\x{2106}'.
'\x{2108}\x{2109}\x{2114}\x{2116}-\x{2118}\x{211e}-\x{2123}\x{2125}\x{2127}'.
'\x{2129}\x{212e}\x{2132}\x{213a}\x{213b}\x{2140}-\x{2144}\x{214a}-\x{2b13}'.
'\x{2ce5}-\x{2cff}\x{2d6f}\x{2e00}-\x{3005}\x{3007}-\x{303b}\x{303d}-\x{303f}'.
'\x{3099}-\x{309e}\x{30a0}\x{30fb}\x{30fd}\x{30fe}\x{3190}-\x{319f}\x{31c0}-'.
'\x{31cf}\x{3200}-\x{33ff}\x{4dc0}-\x{4dff}\x{a015}\x{a490}-\x{a716}\x{a802}'.
'\x{a806}\x{a80b}\x{a823}-\x{a82b}\x{d800}-\x{f8ff}\x{fb1e}\x{fb29}\x{fd3e}'.
'\x{fd3f}\x{fdfc}-\x{fe6b}\x{feff}-\x{ff0f}\x{ff1a}-\x{ff20}\x{ff3b}-\x{ff40}'.
'\x{ff5b}-\x{ff65}\x{ff70}\x{ff9e}\x{ff9f}\x{ffe0}-\x{fffd}');

/**
 * Matches all 'N' Unicode character classes (numbers)
 */
define('PREG_CLASS_NUMBERS',
'\x{30}-\x{39}\x{b2}\x{b3}\x{b9}\x{bc}-\x{be}\x{660}-\x{669}\x{6f0}-\x{6f9}'.
'\x{966}-\x{96f}\x{9e6}-\x{9ef}\x{9f4}-\x{9f9}\x{a66}-\x{a6f}\x{ae6}-\x{aef}'.
'\x{b66}-\x{b6f}\x{be7}-\x{bf2}\x{c66}-\x{c6f}\x{ce6}-\x{cef}\x{d66}-\x{d6f}'.
'\x{e50}-\x{e59}\x{ed0}-\x{ed9}\x{f20}-\x{f33}\x{1040}-\x{1049}\x{1369}-'.
'\x{137c}\x{16ee}-\x{16f0}\x{17e0}-\x{17e9}\x{17f0}-\x{17f9}\x{1810}-\x{1819}'.
'\x{1946}-\x{194f}\x{2070}\x{2074}-\x{2079}\x{2080}-\x{2089}\x{2153}-\x{2183}'.
'\x{2460}-\x{249b}\x{24ea}-\x{24ff}\x{2776}-\x{2793}\x{3007}\x{3021}-\x{3029}'.
'\x{3038}-\x{303a}\x{3192}-\x{3195}\x{3220}-\x{3229}\x{3251}-\x{325f}\x{3280}-'.
'\x{3289}\x{32b1}-\x{32bf}\x{ff10}-\x{ff19}');

/**
 * Matches all 'P' Unicode character classes (punctuation)
 */
define('PREG_CLASS_PUNCTUATION',
'\x{21}-\x{23}\x{25}-\x{2a}\x{2c}-\x{2f}\x{3a}\x{3b}\x{3f}\x{40}\x{5b}-\x{5d}'.
'\x{5f}\x{7b}\x{7d}\x{a1}\x{ab}\x{b7}\x{bb}\x{bf}\x{37e}\x{387}\x{55a}-\x{55f}'.
'\x{589}\x{58a}\x{5be}\x{5c0}\x{5c3}\x{5f3}\x{5f4}\x{60c}\x{60d}\x{61b}\x{61f}'.
'\x{66a}-\x{66d}\x{6d4}\x{700}-\x{70d}\x{964}\x{965}\x{970}\x{df4}\x{e4f}'.
'\x{e5a}\x{e5b}\x{f04}-\x{f12}\x{f3a}-\x{f3d}\x{f85}\x{104a}-\x{104f}\x{10fb}'.
'\x{1361}-\x{1368}\x{166d}\x{166e}\x{169b}\x{169c}\x{16eb}-\x{16ed}\x{1735}'.
'\x{1736}\x{17d4}-\x{17d6}\x{17d8}-\x{17da}\x{1800}-\x{180a}\x{1944}\x{1945}'.
'\x{2010}-\x{2027}\x{2030}-\x{2043}\x{2045}-\x{2051}\x{2053}\x{2054}\x{2057}'.
'\x{207d}\x{207e}\x{208d}\x{208e}\x{2329}\x{232a}\x{23b4}-\x{23b6}\x{2768}-'.
'\x{2775}\x{27e6}-\x{27eb}\x{2983}-\x{2998}\x{29d8}-\x{29db}\x{29fc}\x{29fd}'.
'\x{3001}-\x{3003}\x{3008}-\x{3011}\x{3014}-\x{301f}\x{3030}\x{303d}\x{30a0}'.
'\x{30fb}\x{fd3e}\x{fd3f}\x{fe30}-\x{fe52}\x{fe54}-\x{fe61}\x{fe63}\x{fe68}'.
'\x{fe6a}\x{fe6b}\x{ff01}-\x{ff03}\x{ff05}-\x{ff0a}\x{ff0c}-\x{ff0f}\x{ff1a}'.
'\x{ff1b}\x{ff1f}\x{ff20}\x{ff3b}-\x{ff3d}\x{ff3f}\x{ff5b}\x{ff5d}\x{ff5f}-'.
'\x{ff65}');

/**
 * Matches all CJK characters that are candidates for auto-splitting
 * (Chinese, Japanese, Korean).
 * Contains kana and BMP ideographs.
 */
define('PREG_CLASS_CJK', '\x{3041}-\x{30ff}\x{31f0}-\x{31ff}\x{3400}-\x{4db5}'.
'\x{4e00}-\x{9fbb}\x{f900}-\x{fad9}');

/**
 * Implementation of hook_help().
 */
function search_help($path, $arg) {
  switch ($path) {
    case 'admin/help#search':
      $output = '<p>'. t('The search module adds the ability to search for content by keywords. Search is often the only practical way to find content on a large site, and is useful for finding both users and posts.') .'</p>';
      $output .= '<p>'. t('To provide keyword searching, the search engine maintains an index of words found in your site\'s content. To build and maintain this index, a correctly configured <a href="@cron">cron maintenance task</a> is required. Indexing behavior can be adjusted using the <a href="@searchsettings">search settings page</a>; for example, the <em>Number of items to index per cron run</em> sets the maximum number of items indexed in each pass of a <a href="@cron">cron maintenance task</a>. If necessary, reduce this number to prevent timeouts and memory errors when indexing.', array('@cron' => url('admin/reports/status'), '@searchsettings' => url('admin/settings/search'))) .'</p>';
      $output .= '<p>'. t('For more information, see the online handbook entry for <a href="@search">Search module</a>.', array('@search' => 'http://drupal.org/handbook/modules/search/')) .'</p>';
      return $output;
    case 'admin/settings/search':
      return '<p>'. t('The search engine maintains an index of words found in your site\'s content. To build and maintain this index, a correctly configured <a href="@cron">cron maintenance task</a> is required. Indexing behavior can be adjusted using the settings below.', array('@cron' => url('admin/reports/status'))) .'</p>';
    case 'search#noresults':
      return t('<ul>
<li>Check if your spelling is correct.</li>
<li>Remove quotes around phrases to match each word individually: <em>"blue smurf"</em> will match less than <em>blue smurf</em>.</li>
<li>Consider loosening your query with <em>OR</em>: <em>blue smurf</em> will match less than <em>blue OR smurf</em>.</li>
</ul>');
  }
}

/**
 * Implementation of hook_theme()
 */
function search_theme() {
  return array(
    'search_theme_form' => array(
      'arguments' => array('form' => NULL),
      'template' => 'search-theme-form',
    ),
    'search_block_form' => array(
      'arguments' => array('form' => NULL),
      'template' => 'search-block-form',
    ),
    'search_result' => array(
      'arguments' => array('result' => NULL, 'type' => NULL),
      'file' => 'search.pages.inc',
      'template' => 'search-result',
    ),
    'search_results' => array(
      'arguments' => array('results' => NULL, 'type' => NULL),
      'file' => 'search.pages.inc',
      'template' => 'search-results',
    ),
  );
}

/**
 * Implementation of hook_perm().
 */
function search_perm() {
  return array('search content', 'use advanced search', 'administer search');
}

/**
 * Implementation of hook_block().
 */
function search_block($op = 'list', $delta = 0) {
  if ($op == 'list') {
    $blocks[0]['info'] = t('Search form');
    // Not worth caching.
    $blocks[0]['cache'] = BLOCK_NO_CACHE;
    return $blocks;
  }
  else if ($op == 'view' && user_access('search content')) {
    $block['content'] = drupal_get_form('search_block_form');
    $block['subject'] = t('Search');
    return $block;
  }
}

/**
 * Implementation of hook_menu().
 */
function search_menu() {
  $items['search'] = array(
    'title' => 'Search',
    'page callback' => 'search_view',
    'access arguments' => array('search content'),
    'type' => MENU_SUGGESTED_ITEM,
    'file' => 'search.pages.inc',
  );
  $items['admin/settings/search'] = array(
    'title' => 'Search settings',
    'description' => 'Configure relevance settings for search and other indexing options',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('search_admin_settings'),
    'access arguments' => array('administer search'),
    'type' => MENU_NORMAL_ITEM,
    'file' => 'search.admin.inc',
  );
  $items['admin/settings/search/wipe'] = array(
    'title' => 'Clear index',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('search_wipe_confirm'),
    'access arguments' => array('administer search'),
    'type' => MENU_CALLBACK,
    'file' => 'search.admin.inc',
  );
  $items['admin/reports/search'] = array(
    'title' => 'Top search phrases',
    'description' => 'View most popular search phrases.',
    'page callback' => 'dblog_top',
    'page arguments' => array('search'),
    'access arguments' => array('access site reports'),
    'file' => 'dblog.admin.inc',
    'file path' => drupal_get_path('module', 'dblog'),
  );

  foreach (module_implements('search') as $name) {
    $items['search/'. $name .'/%menu_tail'] = array(
      'title callback' => 'module_invoke',
      'title arguments' => array($name, 'search', 'name', TRUE),
      'page callback' => 'search_view',
      'page arguments' => array($name),
      'access callback' => '_search_menu',
      'access arguments' => array($name),
      'type' => MENU_LOCAL_TASK,
      'parent' => 'search',
      'file' => 'search.pages.inc',
    );
  }
  return $items;
}

function _search_menu($name) {
  return user_access('search content') && module_invoke($name, 'search', 'name');
}

/**
 * Wipes a part of or the entire search index.
 *
 * @param $sid
 *  (optional) The SID of the item to wipe. If specified, $type must be passed
 *  too.
 * @param $type
 *  (optional) The type of item to wipe.
 */
function search_wipe($sid = NULL, $type = NULL, $reindex = FALSE) {
  if ($type == NULL && $sid == NULL) {
    module_invoke_all('search', 'reset');
  }
  else {
    db_query("DELETE FROM {search_dataset} WHERE sid = %d AND type = '%s'", $sid, $type);
    db_query("DELETE FROM {search_index} WHERE sid = %d AND type = '%s'", $sid, $type);
    // Don't remove links if re-indexing.
    if (!$reindex) {
      db_query("DELETE FROM {search_node_links} WHERE sid = %d AND type = '%s'", $sid, $type);
    }
  }
}

/**
 * Marks a word as dirty (or retrieves the list of dirty words). This is used
 * during indexing (cron). Words which are dirty have outdated total counts in
 * the search_total table, and need to be recounted.
 */
function search_dirty($word = NULL) {
  static $dirty = array();
  if ($word !== NULL) {
    $dirty[$word] = TRUE;
  }
  else {
    return $dirty;
  }
}

/**
 * Implementation of hook_cron().
 *
 * Fires hook_update_index() in all modules and cleans up dirty words (see
 * search_dirty).
 */
function search_cron() {
  // We register a shutdown function to ensure that search_total is always up
  // to date.
  register_shutdown_function('search_update_totals');

  // Update word index
  foreach (module_list() as $module) {
    module_invoke($module, 'update_index');
  }
}

/**
 * This function is called on shutdown to ensure that search_total is always
 * up to date (even if cron times out or otherwise fails).
 */
function search_update_totals() {
  // Update word IDF (Inverse Document Frequency) counts for new/changed words
  foreach (search_dirty() as $word => $dummy) {
    // Get total count
    $total = db_result(db_query("SELECT SUM(score) FROM {search_index} WHERE word = '%s'", $word));
    // Apply Zipf's law to equalize the probability distribution
    $total = log10(1 + 1/(max(1, $total)));
    db_query("UPDATE {search_total} SET count = %f WHERE word = '%s'", $total, $word);
    if (!db_affected_rows()) {
      @db_query("INSERT INTO {search_total} (word, count) VALUES ('%s', %f)", $word, $total);
    }
  }
  // Find words that were deleted from search_index, but are still in
  // search_total. We use a LEFT JOIN between the two tables and keep only the
  // rows which fail to join.
  $result = db_query("SELECT t.word AS realword, i.word FROM {search_total} t LEFT JOIN {search_index} i ON t.word = i.word WHERE i.word IS NULL");
  while ($word = db_fetch_object($result)) {
    db_query("DELETE FROM {search_total} WHERE word = '%s'", $word->realword);
  }
}

/**
 * Simplifies a string according to indexing rules.
 */
function search_simplify($text) {
  // Decode entities to UTF-8
  $text = decode_entities($text);

  // Lowercase
  $text = drupal_strtolower($text);

  // Call an external processor for word handling.
  search_invoke_preprocess($text);

  // Simple CJK handling
  if (variable_get('overlap_cjk', TRUE)) {
    $text = preg_replace_callback('/['. PREG_CLASS_CJK .']+/u', 'search_expand_cjk', $text);
  }

  // To improve searching for numerical data such as dates, IP addresses
  // or version numbers, we consider a group of numerical characters
  // separated only by punctuation characters to be one piece.
  // This also means that searching for e.g. '20/03/1984' also returns
  // results with '20-03-1984' in them.
  // Readable regexp: ([number]+)[punctuation]+(?=[number])
  $text = preg_replace('/(['. PREG_CLASS_NUMBERS .']+)['. PREG_CLASS_PUNCTUATION .']+(?=['. PREG_CLASS_NUMBERS .'])/u', '\1', $text);

  // The dot, underscore and dash are simply removed. This allows meaningful
  // search behavior with acronyms and URLs.
  $text = preg_replace('/[._-]+/', '', $text);

  // With the exception of the rules above, we consider all punctuation,
  // marks, spacers, etc, to be a word boundary.
  $text = preg_replace('/['. PREG_CLASS_SEARCH_EXCLUDE .']+/u', ' ', $text);

  return $text;
}

/**
 * Basic CJK tokenizer. Simply splits a string into consecutive, overlapping
 * sequences of characters ('minimum_word_size' long).
 */
function search_expand_cjk($matches) {
  $min = variable_get('minimum_word_size', 3);
  $str = $matches[0];
  $l = drupal_strlen($str);
  // Passthrough short words
  if ($l <= $min) {
    return ' '. $str .' ';
  }
  $tokens = ' ';
  // FIFO queue of characters
  $chars = array();
  // Begin loop
  for ($i = 0; $i < $l; ++$i) {
    // Grab next character
    $current = drupal_substr($str, 0, 1);
    $str = substr($str, strlen($current));
    $chars[] = $current;
    if ($i >= $min - 1) {
      $tokens .= implode('', $chars) .' ';
      array_shift($chars);
    }
  }
  return $tokens;
}

/**
 * Splits a string into tokens for indexing.
 */
function search_index_split($text) {
  static $last = NULL;
  static $lastsplit = NULL;

  if ($last == $text) {
    return $lastsplit;
  }
  // Process words
  $text = search_simplify($text);
  $words = explode(' ', $text);
  array_walk($words, '_search_index_truncate');

  // Save last keyword result
  $last = $text;
  $lastsplit = $words;

  return $words;
}

/**
 * Helper function for array_walk in search_index_split.
 */
function _search_index_truncate(&$text) {
  $text = truncate_utf8($text, 50);
}

/**
 * Invokes hook_search_preprocess() in modules.
 */
function search_invoke_preprocess(&$text) {
  foreach (module_implements('search_preprocess') as $module) {
    $text = module_invoke($module, 'search_preprocess', $text);
  }
}

/**
 * Update the full-text search index for a particular item.
 *
 * @param $sid
 *   A number identifying this particular item (e.g. node id).
 *
 * @param $type
 *   A string defining this type of item (e.g. 'node')
 *
 * @param $text
 *   The content of this item. Must be a piece of HTML text.
 *
 * @ingroup search
 */
function search_index($sid, $type, $text) {
  $minimum_word_size = variable_get('minimum_word_size', 3);

  // Link matching
  global $base_url;
  $node_regexp = '@href=[\'"]?(?:'. preg_quote($base_url, '@') .'/|'. preg_quote(base_path(), '@') .')(?:\?q=)?/?((?![a-z]+:)[^\'">]+)[\'">]@i';

  // Multipliers for scores of words inside certain HTML tags.
  // Note: 'a' must be included for link ranking to work.
  $tags = array('h1' => 25,
                'h2' => 18,
                'h3' => 15,
                'h4' => 12,
                'h5' => 9,
                'h6' => 6,
                'u' => 3,
                'b' => 3,
                'i' => 3,
                'strong' => 3,
                'em' => 3,
                'a' => 10);

  // Strip off all ignored tags to speed up processing, but insert space before/after
  // them to keep word boundaries.
  $text = str_replace(array('<', '>'), array(' <', '> '), $text);
  $text = strip_tags($text, '<'. implode('><', array_keys($tags)) .'>');

  // Split HTML tags from plain text.
  $split = preg_split('/\s*<([^>]+?)>\s*/', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
  // Note: PHP ensures the array consists of alternating delimiters and literals
  // and begins and ends with a literal (inserting $null as required).

  $tag = FALSE; // Odd/even counter. Tag or no tag.
  $link = FALSE; // State variable for link analyser
  $score = 1; // Starting score per word
  $accum = ' '; // Accumulator for cleaned up data
  $tagstack = array(); // Stack with open tags
  $tagwords = 0; // Counter for consecutive words
  $focus = 1; // Focus state

  $results = array(0 => array()); // Accumulator for words for index

  foreach ($split as $value) {
    if ($tag) {
      // Increase or decrease score per word based on tag
      list($tagname) = explode(' ', $value, 2);
      $tagname = drupal_strtolower($tagname);
      // Closing or opening tag?
      if ($tagname[0] == '/') {
        $tagname = substr($tagname, 1);
        // If we encounter unexpected tags, reset score to avoid incorrect boosting.
        if (!count($tagstack) || $tagstack[0] != $tagname) {
          $tagstack = array();
          $score = 1;
        }
        else {
          // Remove from tag stack and decrement score
          $score = max(1, $score - $tags[array_shift($tagstack)]);
        }
        if ($tagname == 'a') {
          $link = FALSE;
        }
      }
      else {
        if (isset($tagstack[0]) && $tagstack[0] == $tagname) {
          // None of the tags we look for make sense when nested identically.
          // If they are, it's probably broken HTML.
          $tagstack = array();
          $score = 1;
        }
        else {
          // Add to open tag stack and increment score
          array_unshift($tagstack, $tagname);
          $score += $tags[$tagname];
        }
        if ($tagname == 'a') {
          // Check if link points to a node on this site
          if (preg_match($node_regexp, $value, $match)) {
            $path = drupal_get_normal_path($match[1]);
            if (preg_match('!(?:node|book)/(?:view/)?([0-9]+)!i', $path, $match)) {
              $linknid = $match[1];
              if ($linknid > 0) {
                // Note: ignore links to uncachable nodes to avoid redirect bugs.
                $node = db_fetch_object(db_query('SELECT n.title, n.nid, n.vid, r.format FROM {node} n INNER JOIN {node_revisions} r ON n.vid = r.vid WHERE n.nid = %d', $linknid));
                if (filter_format_allowcache($node->format)) {
                  $link = TRUE;
                  $linktitle = $node->title;
                }
              }
            }
          }
        }
      }
      // A tag change occurred, reset counter.
      $tagwords = 0;
    }
    else {
      // Note: use of PREG_SPLIT_DELIM_CAPTURE above will introduce empty values
      if ($value != '') {
        if ($link) {
          // Check to see if the node link text is its URL. If so, we use the target node title instead.
          if (preg_match('!^https?://!i', $value)) {
            $value = $linktitle;
          }
        }
        $words = search_index_split($value);
        foreach ($words as $word) {
          // Add word to accumulator
          $accum .= $word .' ';
          $num = is_numeric($word);
          // Check wordlength
          if ($num || drupal_strlen($word) >= $minimum_word_size) {
            // Normalize numbers
            if ($num) {
              $word = (int)ltrim($word, '-0');
            }

            // Links score mainly for the target.
            if ($link) {
              if (!isset($results[$linknid])) {
                $results[$linknid] = array();
              }
              $results[$linknid][] = $word;
              // Reduce score of the link caption in the source.
              $focus *= 0.2;
            }
            // Fall-through
            if (!isset($results[0][$word])) {
              $results[0][$word] = 0;
            }
            $results[0][$word] += $score * $focus;

            // Focus is a decaying value in terms of the amount of unique words up to this point.
            // From 100 words and more, it decays, to e.g. 0.5 at 500 words and 0.3 at 1000 words.
            $focus = min(1, .01 + 3.5 / (2 + count($results[0]) * .015));
          }
          $tagwords++;
          // Too many words inside a single tag probably mean a tag was accidentally left open.
          if (count($tagstack) && $tagwords >= 15) {
            $tagstack = array();
            $score = 1;
          }
        }
      }
    }
    $tag = !$tag;
  }

  search_wipe($sid, $type, TRUE);

  // Insert cleaned up data into dataset
  db_query("INSERT INTO {search_dataset} (sid, type, data, reindex) VALUES (%d, '%s', '%s', %d)", $sid, $type, $accum, 0);

  // Insert results into search index
  foreach ($results[0] as $word => $score) {
    // Try inserting first because this will succeed most times, but because
    // the database collates similar words (accented and non-accented), the
    // insert can fail, in which case we need to add the word scores together.
    @db_query("INSERT INTO {search_index} (word, sid, type, score) VALUES ('%s', %d, '%s', %f)", $word, $sid, $type, $score);
    if (!db_affected_rows()) {
      db_query("UPDATE {search_index} SET score = score + %f WHERE word = '%s' AND sid = %d AND type = '%s'", $score, $word, $sid, $type);
    }
    search_dirty($word);
  }
  unset($results[0]);

  // Get all previous links from this item.
  $result = db_query("SELECT nid, caption FROM {search_node_links} WHERE sid = %d AND type = '%s'", $sid, $type);
  $links = array();
  while ($link = db_fetch_object($result)) {
    $links[$link->nid] = $link->caption;
  }

  // Now store links to nodes.
  foreach ($results as $nid => $words) {
    $caption = implode(' ', $words);
    if (isset($links[$nid])) {
      if ($links[$nid] != $caption) {
        // Update the existing link and mark the node for reindexing.
        db_query("UPDATE {search_node_links} SET caption = '%s' WHERE sid = %d AND type = '%s' AND nid = %d", $caption, $sid, $type, $nid);
        search_touch_node($nid);
      }
      // Unset the link to mark it as processed.
      unset($links[$nid]);
    }
    else {
      // Insert the existing link and mark the node for reindexing.
      db_query("INSERT INTO {search_node_links} (caption, sid, type, nid) VALUES ('%s', %d, '%s', %d)", $caption, $sid, $type, $nid);
      search_touch_node($nid);
    }
  }
  // Any left-over links in $links no longer exist. Delete them and mark the nodes for reindexing.
  foreach ($links as $nid => $caption) {
    db_query("DELETE FROM {search_node_links} WHERE sid = %d AND type = '%s' AND nid = %d", $sid, $type, $nid);
    search_touch_node($nid);
  }
}

/**
 * Change a node's changed timestamp to 'now' to force reindexing.
 *
 * @param $nid
 *   The nid of the node that needs reindexing.
 */
function search_touch_node($nid) {
  db_query("UPDATE {search_dataset} SET reindex = %d WHERE sid = %d AND type = 'node'", time(), $nid);
}

/**
 * Implementation of hook_nodeapi().
 */
function search_nodeapi(&$node, $op, $teaser = NULL, $page = NULL) {
  switch ($op) {
    // Transplant links to a node into the target node.
    case 'update index':
      $result = db_query("SELECT caption FROM {search_node_links} WHERE nid = %d", $node->nid);
      $output = array();
      while ($link = db_fetch_object($result)) {
        $output[] = $link->caption;
      }
      if (count($output)) {
        return '<a>('. implode(', ', $output) .')</a>';
      }
      break;
    // Reindex the node when it is updated.  The node is automatically indexed
    // when it is added, simply by being added to the node table.
    case 'update':
      search_touch_node($node->nid);
      break;
  }
}

/**
 * Implementation of hook_comment().
 */
function search_comment($a1, $op) {
  switch ($op) {
    // Reindex the node when comments are added or changed
    case 'insert':
    case 'update':
    case 'delete':
    case 'publish':
    case 'unpublish':
      search_touch_node(is_array($a1) ? $a1['nid'] : $a1->nid);
      break;
  }
}

/**
 * Extract a module-specific search option from a search query. e.g. 'type:book'
 */
function search_query_extract($keys, $option) {
  if (preg_match('/(^| )'. $option .':([^ ]*)( |$)/i', $keys, $matches)) {
    return $matches[2];
  }
}

/**
 * Return a query with the given module-specific search option inserted in.
 * e.g. 'type:book'.
 */
function search_query_insert($keys, $option, $value = '') {
  if (search_query_extract($keys, $option)) {
    $keys = trim(preg_replace('/(^| )'. $option .':[^ ]*/i', '', $keys));
  }
  if ($value != '') {
    $keys .= ' '. $option .':'. $value;
  }
  return $keys;
}

/**
 * Parse a search query into SQL conditions.
 *
 * We build two queries that matches the dataset bodies. @See do_search for
 * more about these.
 *
 * @param $text
 *   The search keys.
 * @return
 *   A list of six elements.
 *    * A series of statements AND'd together which will be used to provide all
 *      possible matches.
 *    * Arguments for this query part.
 *    * A series of exact word matches OR'd together.
 *    * Arguments for this query part.
 *    * A bool indicating whether this is a simple query or not. Negative
 *      terms, presence of both AND / OR make this FALSE.
 *    * A bool indicating the presence of a lowercase or. Maybe the user
 *      wanted to use OR.
 */
function search_parse_query($text) {
  $keys = array('positive' => array(), 'negative' => array());

  // Tokenize query string
  preg_match_all('/ (-?)("[^"]+"|[^" ]+)/i', ' '. $text, $matches, PREG_SET_ORDER);

  if (count($matches) < 1) {
    return NULL;
  }

  // Classify tokens
  $or = FALSE;
  $warning = '';
  $simple = TRUE;
  foreach ($matches as $match) {
    $phrase = FALSE;
    // Strip off phrase quotes
    if ($match[2]{0} == '"') {
      $match[2] = substr($match[2], 1, -1);
      $phrase = TRUE;
      $simple = FALSE;
    }
    // Simplify keyword according to indexing rules and external preprocessors
    $words = search_simplify($match[2]);
    // Re-explode in case simplification added more words, except when matching a phrase
    $words = $phrase ? array($words) : preg_split('/ /', $words, -1, PREG_SPLIT_NO_EMPTY);
    // Negative matches
    if ($match[1] == '-') {
      $keys['negative'] = array_merge($keys['negative'], $words);
    }
    // OR operator: instead of a single keyword, we store an array of all
    // OR'd keywords.
    elseif ($match[2] == 'OR' && count($keys['positive'])) {
      $last = array_pop($keys['positive']);
      // Starting a new OR?
      if (!is_array($last)) {
        $last = array($last);
      }
      $keys['positive'][] = $last;
      $or = TRUE;
      continue;
    }
    // AND operator: implied, so just ignore it
    elseif ($match[2] == 'AND' || $match[2] == 'and') {
      $warning = $match[2];
      continue;
    }

    // Plain keyword
    else {
      if ($match[2] == 'or') {
        $warning = $match[2];
      }
      if ($or) {
        // Add to last element (which is an array)
        $keys['positive'][count($keys['positive']) - 1] = array_merge($keys['positive'][count($keys['positive']) - 1], $words);
      }
      else {
        $keys['positive'] = array_merge($keys['positive'], $words);
      }
    }
    $or = FALSE;
  }

  // Convert keywords into SQL statements.
  $query = array();
  $query2 = array();
  $arguments = array();
  $arguments2 = array();
  $matches = 0;
  $simple_and = FALSE;
  $simple_or = FALSE;
  // Positive matches
  foreach ($keys['positive'] as $key) {
    // Group of ORed terms
    if (is_array($key) && count($key)) {
      $simple_or = TRUE;
      $queryor = array();
      $any = FALSE;
      foreach ($key as $or) {
        list($q, $num_new_scores) = _search_parse_query($or, $arguments2);
        $any |= $num_new_scores;
        if ($q) {
          $queryor[] = $q;
          $arguments[] = $or;
        }
      }
      if (count($queryor)) {
        $query[] = '('. implode(' OR ', $queryor) .')';
        // A group of OR keywords only needs to match once
        $matches += ($any > 0);
      }
    }
    // Single ANDed term
    else {
      $simple_and = TRUE;
      list($q, $num_new_scores, $num_valid_words) = _search_parse_query($key, $arguments2);
      if ($q) {
        $query[] = $q;
        $arguments[] = $key;
        if (!$num_valid_words) {
          $simple = FALSE;
        }
        // Each AND keyword needs to match at least once
        $matches += $num_new_scores;
      }
    }
  }
  if ($simple_and && $simple_or) {
    $simple = FALSE;
  }
  // Negative matches
  foreach ($keys['negative'] as $key) {
    list($q) = _search_parse_query($key, $arguments2, TRUE);
    if ($q) {
      $query[] = $q;
      $arguments[] = $key;
      $simple = FALSE;
    }
  }
  $query = implode(' AND ', $query);

  // Build word-index conditions for the first pass
  $query2 = substr(str_repeat("i.word = '%s' OR ", count($arguments2)), 0, -4);

  return array($query, $arguments, $query2, $arguments2, $matches, $simple, $warning);
}

/**
 * Helper function for search_parse_query();
 */
function _search_parse_query(&$word, &$scores, $not = FALSE) {
  $num_new_scores = 0;
  $num_valid_words = 0;
  // Determine the scorewords of this word/phrase
  if (!$not) {
    $split = explode(' ', $word);
    foreach ($split as $s) {
      $num = is_numeric($s);
      if ($num || drupal_strlen($s) >= variable_get('minimum_word_size', 3)) {
        $s = $num ? ((int)ltrim($s, '-0')) : $s;
        if (!isset($scores[$s])) {
          $scores[$s] = $s;
          $num_new_scores++;
        }
        $num_valid_words++;
      }
    }
  }
  // Return matching snippet and number of added words
  return array("d.data ". ($not ? 'NOT ' : '') ."LIKE '%% %s %%'", $num_new_scores, $num_valid_words);
}

/**
 * Do a query on the full-text search index for a word or words.
 *
 * This function is normally only called by each module that support the
 * indexed search (and thus, implements hook_update_index()).
 *
 * Results are retrieved in two logical passes. However, the two passes are
 * joined together into a single query.  And in the case of most simple
 * queries the second pass is not even used.
 *
 * The first pass selects a set of all possible matches, which has the benefit
 * of also providing the exact result set for simple "AND" or "OR" searches.
 *
 * The second portion of the query further refines this set by verifying
 * advanced text conditions (such negative or phrase matches)
 *
 * @param $keywords
 *   A search string as entered by the user.
 *
 * @param $type
 *   A string identifying the calling module.
 *
 * @param $join1
 *   (optional) Inserted into the JOIN part of the first SQL query.
 *   For example "INNER JOIN {node} n ON n.nid = i.sid".
 *
 * @param $where1
 *   (optional) Inserted into the WHERE part of the first SQL query.
 *   For example "(n.status > %d)".
 *
 * @param $arguments1
 *   (optional) Extra SQL arguments belonging to the first query.
 *
 * @param $columns2
 *   (optional) Inserted into the SELECT pat of the second query. Must contain
 *   a column selected as 'score'.
 *   defaults to 'i.relevance AS score'
 *
 * @param $join2
 *   (optional) Inserted into the JOIN par of the second SQL query.
 *   For example "INNER JOIN {node_comment_statistics} n ON n.nid = i.sid"
 *
 * @param $arguments2
 *   (optional) Extra SQL arguments belonging to the second query parameter.
 *
 * @param $sort_parameters
 *   (optional) SQL arguments for sorting the final results.
 *              Default: 'ORDER BY score DESC'
 *
 * @return
 *   An array of objects for the search results.
 *
 * @ingroup search
 */
function do_search($keywords, $type, $join1 = '', $where1 = '1 = 1', $arguments1 = array(), $columns2 = 'i.relevance AS score', $join2 = '', $arguments2 = array(), $sort_parameters = 'ORDER BY score DESC') {
  $query = search_parse_query($keywords);

  if ($query[2] == '') {
    form_set_error('keys', t('You must include at least one positive keyword with @count characters or more.', array('@count' => variable_get('minimum_word_size', 3))));
  }
  if ($query[6]) {
    if ($query[6] == 'or') {
      drupal_set_message(t('Search for either of the two terms with uppercase <strong>OR</strong>. For example, <strong>cats OR dogs</strong>.'));
    }
  }
  if ($query === NULL || $query[0] == '' || $query[2] == '') {
    return array();
  }

  // Build query for keyword normalization.
  $conditions = "$where1 AND ($query[2]) AND i.type = '%s'";
  $arguments1 = array_merge($arguments1, $query[3], array($type));
  $join = "INNER JOIN {search_total} t ON i.word = t.word $join1";
  if (!$query[5]) {
    $conditions .= " AND ($query[0])";
    $arguments1 = array_merge($arguments1, $query[1]);
    $join .= " INNER JOIN {search_dataset} d ON i.sid = d.sid AND i.type = d.type";
  }

  // Calculate maximum keyword relevance, to normalize it.
  $select = "SELECT SUM(i.score * t.count) AS score FROM {search_index} i $join WHERE $conditions GROUP BY i.type, i.sid HAVING COUNT(*) >= %d ORDER BY score DESC";
  $arguments = array_merge($arguments1, array($query[4]));
  $normalize = db_result(db_query_range($select, $arguments, 0, 1));
  if (!$normalize) {
    return array();
  }
  $columns2 = str_replace('i.relevance', '('. (1.0 / $normalize) .' * SUM(i.score * t.count))', $columns2);

  // Build query to retrieve results.
  $select = "SELECT i.type, i.sid, $columns2 FROM {search_index} i $join $join2 WHERE $conditions GROUP BY i.type, i.sid HAVING COUNT(*) >= %d";
  $count_select =  "SELECT COUNT(*) FROM ($select) n1";
  $arguments = array_merge($arguments2, $arguments1, array($query[4]));

  // Do actual search query
  $result = pager_query("$select $sort_parameters", 10, 0, $count_select, $arguments);
  $results = array();
  while ($item = db_fetch_object($result)) {
    $results[] = $item;
  }
  return $results;
}

/**
 * Helper function for grabbing search keys.
 */
function search_get_keys() {
  static $return;
  if (!isset($return)) {
    // Extract keys as remainder of path
    // Note: support old GET format of searches for existing links.
    $path = explode('/', $_GET['q'], 3);
    $keys = empty($_REQUEST['keys']) ? '' : $_REQUEST['keys'];
    $return = count($path) == 3 ? $path[2] : $keys;
  }
  return $return;
}

/**
 * @defgroup search Search interface
 * @{
 * The Drupal search interface manages a global search mechanism.
 *
 * Modules may plug into this system to provide searches of different types of
 * data. Most of the system is handled by search.module, so this must be enabled
 * for all of the search features to work.
 *
 * There are three ways to interact with the search system:
 * - Specifically for searching nodes, you can implement
 *   hook_nodeapi('update index') and hook_nodeapi('search result'). However,
 *   note that the search system already indexes all visible output of a node,
 *   i.e. everything displayed normally by hook_view() and hook_nodeapi('view').
 *   This is usually sufficient. You should only use this mechanism if you want
 *   additional, non-visible data to be indexed.
 * - Implement hook_search(). This will create a search tab for your module on
 *   the /search page with a simple keyword search form.
 * - Implement hook_update_index(). This allows your module to use Drupal's
 *   HTML indexing mechanism for searching full text efficiently.
 *
 * If your module needs to provide a more complicated search form, then you need
 * to implement it yourself without hook_search(). In that case, you should
 * define it as a local task (tab) under the /search page (e.g. /search/mymodule)
 * so that users can easily find it.
 */

/**
 * Render a search form.
 *
 * @param $action
 *   Form action. Defaults to "search".
 * @param $keys
 *   The search string entered by the user, containing keywords for the search.
 * @param $type
 *   The type of search to render the node for. Must be the name of module
 *   which implements hook_search(). Defaults to 'node'.
 * @param $prompt
 *   A piece of text to put before the form (e.g. "Enter your keywords")
 * @return
 *   A Form API array for the search form.
 */
function search_form(&$form_state, $action = '', $keys = '', $type = NULL, $prompt = NULL) {

  // Add CSS
  drupal_add_css(drupal_get_path('module', 'search') .'/search.css', 'module', 'all', FALSE);

  if (!$action) {
    $action = url('search/'. $type);
  }
  if (is_null($prompt)) {
    $prompt = t('Enter your keywords');
  }

  $form = array(
    '#action' => $action,
    '#attributes' => array('class' => 'search-form'),
  );
  $form['module'] = array('#type' => 'value', '#value' => $type);
  $form['basic'] = array('#type' => 'item', '#title' => $prompt, '#id' => 'edit-keys');
  $form['basic']['inline'] = array('#prefix' => '<div class="container-inline">', '#suffix' => '</div>');
  $form['basic']['inline']['keys'] = array(
    '#type' => 'textfield',
    '#title' => '',
    '#default_value' => $keys,
    '#size' => $prompt ? 40 : 20,
    '#maxlength' => 255,
  );
  // processed_keys is used to coordinate keyword passing between other forms
  // that hook into the basic search form.
  $form['basic']['inline']['processed_keys'] = array('#type' => 'value', '#value' => array());
  $form['basic']['inline']['submit'] = array('#type' => 'submit', '#value' => t('Search'));

  return $form;
}

/**
 * Form builder; Output a search form for the search block and the theme's search box.
 *
 * @ingroup forms
 * @see search_box_form_submit()
 * @see theme_search_box_form()
 */
function search_box(&$form_state, $form_id) {
  $form[$form_id] = array(
    '#title' => t('Search this site'),
    '#type' => 'textfield',
    '#size' => 15,
    '#default_value' => '',
    '#attributes' => array('title' => t('Enter the terms you wish to search for.')),
  );
  $form['submit'] = array('#type' => 'submit', '#value' => t('Search'));
  $form['#submit'][] = 'search_box_form_submit';

  return $form;
}

/**
 * Process a block search form submission.
 */
function search_box_form_submit($form, &$form_state) {
  // The search form relies on control of the redirect destination for its
  // functionality, so we override any static destination set in the request,
  // for example by drupal_access_denied() or drupal_not_found()
  // (see http://drupal.org/node/292565).
  if (isset($_REQUEST['destination'])) {
    unset($_REQUEST['destination']);
  }
  if (isset($_REQUEST['edit']['destination'])) {
    unset($_REQUEST['edit']['destination']);
  }

  $form_id = $form['form_id']['#value'];
  $form_state['redirect'] = 'search/node/'. trim($form_state['values'][$form_id]);
}

/**
 * Process variables for search-theme-form.tpl.php.
 *
 * The $variables array contains the following arguments:
 * - $form
 *
 * @see search-theme-form.tpl.php
 */
function template_preprocess_search_theme_form(&$variables) {
  $variables['search'] = array();
  $hidden = array();
  // Provide variables named after form keys so themers can print each element independently.
  foreach (element_children($variables['form']) as $key) {
    $type = $variables['form'][$key]['#type'];
    if ($type == 'hidden' || $type == 'token') {
      $hidden[] = drupal_render($variables['form'][$key]);
    }
    else {
      $variables['search'][$key] = drupal_render($variables['form'][$key]);
    }
  }
  // Hidden form elements have no value to themers. No need for separation.
  $variables['search']['hidden'] = implode($hidden);
  // Collect all form elements to make it easier to print the whole form.
  $variables['search_form'] = implode($variables['search']);
}

/**
 * Process variables for search-block-form.tpl.php.
 *
 * The $variables array contains the following arguments:
 * - $form
 *
 * @see search-block-form.tpl.php
 */
function template_preprocess_search_block_form(&$variables) {
  $variables['search'] = array();
  $hidden = array();
  // Provide variables named after form keys so themers can print each element independently.
  foreach (element_children($variables['form']) as $key) {
    $type = $variables['form'][$key]['#type'];
    if ($type == 'hidden' || $type == 'token') {
      $hidden[] = drupal_render($variables['form'][$key]);
    }
    else {
      $variables['search'][$key] = drupal_render($variables['form'][$key]);
    }
  }
  // Hidden form elements have no value to themers. No need for separation.
  $variables['search']['hidden'] = implode($hidden);
  // Collect all form elements to make it easier to print the whole form.
  $variables['search_form'] = implode($variables['search']);
}

/**
 * Perform a standard search on the given keys, and return the formatted results.
 */
function search_data($keys = NULL, $type = 'node') {

  if (isset($keys)) {
    if (module_hook($type, 'search')) {
      $results = module_invoke($type, 'search', 'search', $keys);
      if (isset($results) && is_array($results) && count($results)) {
        if (module_hook($type, 'search_page')) {
          return module_invoke($type, 'search_page', $results);
        }
        else {
          return theme('search_results', $results, $type);
        }
      }
    }
  }
}

/**
 * Returns snippets from a piece of text, with certain keywords highlighted.
 * Used for formatting search results.
 *
 * @param $keys
 *   A string containing a search query.
 *
 * @param $text
 *   The text to extract fragments from.
 *
 * @return
 *   A string containing HTML for the excerpt.
 */
function search_excerpt($keys, $text) {
  // We highlight around non-indexable or CJK characters.
  $boundary = '(?:(?<=['. PREG_CLASS_SEARCH_EXCLUDE . PREG_CLASS_CJK .'])|(?=['. PREG_CLASS_SEARCH_EXCLUDE . PREG_CLASS_CJK .']))';

  // Extract positive keywords and phrases
  preg_match_all('/ ("([^"]+)"|(?!OR)([^" ]+))/', ' '. $keys, $matches);
  $keys = array_merge($matches[2], $matches[3]);

  // Prepare text
  $text = ' '. strip_tags(str_replace(array('<', '>'), array(' <', '> '), $text)) .' ';
  array_walk($keys, '_search_excerpt_replace');
  $workkeys = $keys;

  // Extract a fragment per keyword for at most 4 keywords.
  // First we collect ranges of text around each keyword, starting/ending
  // at spaces.
  // If the sum of all fragments is too short, we look for second occurrences.
  $ranges = array();
  $included = array();
  $length = 0;
  while ($length < 256 && count($workkeys)) {
    foreach ($workkeys as $k => $key) {
      if (strlen($key) == 0) {
        unset($workkeys[$k]);
        unset($keys[$k]);
        continue;
      }
      if ($length >= 256) {
        break;
      }
      // Remember occurrence of key so we can skip over it if more occurrences
      // are desired.
      if (!isset($included[$key])) {
        $included[$key] = 0;
      }
      // Locate a keyword (position $p), then locate a space in front (position
      // $q) and behind it (position $s)
      if (preg_match('/'. $boundary . $key . $boundary .'/iu', $text, $match, PREG_OFFSET_CAPTURE, $included[$key])) {
        $p = $match[0][1];
        if (($q = strpos($text, ' ', max(0, $p - 60))) !== FALSE) {
          $end = substr($text, $p, 80);
          if (($s = strrpos($end, ' ')) !== FALSE) {
            $ranges[$q] = $p + $s;
            $length += $p + $s - $q;
            $included[$key] = $p + 1;
          }
          else {
            unset($workkeys[$k]);
          }
        }
        else {
          unset($workkeys[$k]);
        }
      }
      else {
        unset($workkeys[$k]);
      }
    }
  }

  // If we didn't find anything, return the beginning.
  if (count($ranges) == 0) {
    return truncate_utf8($text, 256) .' ...';
  }

  // Sort the text ranges by starting position.
  ksort($ranges);

  // Now we collapse overlapping text ranges into one. The sorting makes it O(n).
  $newranges = array();
  foreach ($ranges as $from2 => $to2) {
    if (!isset($from1)) {
      $from1 = $from2;
      $to1 = $to2;
      continue;
    }
    if ($from2 <= $to1) {
      $to1 = max($to1, $to2);
    }
    else {
      $newranges[$from1] = $to1;
      $from1 = $from2;
      $to1 = $to2;
    }
  }
  $newranges[$from1] = $to1;

  // Fetch text
  $out = array();
  foreach ($newranges as $from => $to) {
    $out[] = substr($text, $from, $to - $from);
  }
  $text = (isset($newranges[0]) ? '' : '... ') . implode(' ... ', $out) .' ...';

  // Highlight keywords. Must be done at once to prevent conflicts ('strong' and '<strong>').
  $text = preg_replace('/'. $boundary .'('. implode('|', $keys) .')'. $boundary .'/iu', '<strong>\0</strong>', $text);
  return $text;
}

/**
 * @} End of "defgroup search".
 */

/**
 * Helper function for array_walk in search_except.
 */
function _search_excerpt_replace(&$text) {
  $text = preg_quote($text, '/');
}

function search_forms() {
  $forms['search_theme_form']= array(
    'callback' => 'search_box',
    'callback arguments' => array('search_theme_form'),
  );
  $forms['search_block_form']= array(
    'callback' => 'search_box',
    'callback arguments' => array('search_block_form'),
  );
  return $forms;
}