ArticleSearch::getSimilarityTerms PHP Method

    function getSimilarityTerms($submissionId)
    {
        // Check whether a search plugin provides terms for a similarity search.
        $searchTerms = array();
        $result = HookRegistry::call('ArticleSearch::getSimilarityTerms', array($submissionId, &$searchTerms));
        // If no plugin implements the hook then use the subject keywords
        // of the submission for a similarity search.
        if ($result === false) {
            // Retrieve the article.
            $publishedArticleDao = DAORegistry::getDAO('PublishedArticleDAO');
            /* @var $publishedArticleDao PublishedArticleDAO */
            $article = $publishedArticleDao->getPublishedArticleByArticleId($submissionId);
            if (is_a($article, 'PublishedArticle')) {
                // Retrieve keywords (if any).
                $searchTerms = $article->getLocalizedSubject();
                // Tokenize keywords.
                $searchTerms = trim(preg_replace('/\\s+/', ' ', strtr($searchTerms, ',;', ' ')));
                if (!empty($searchTerms)) {
                    $searchTerms = explode(' ', $searchTerms);
                }
            }
        }
        return $searchTerms;
    }

 /**
  * @see templates/article/footer.tpl
  */
 function callbackTemplateArticlePageFooter($hookName, $params)
 {
     $smarty =& $params[1];
     $output =& $params[2];
     // Identify similarity terms for the given article.
     $displayedArticle = $smarty->get_template_vars('article');
     $articleId = $displayedArticle->getId();
     import('classes.search.ArticleSearch');
     $articleSearch = new ArticleSearch();
     $searchTerms = $articleSearch->getSimilarityTerms($articleId);
     if (empty($searchTerms)) {
         return false;
     }
     // If we got similarity terms then execute a search with...
     // ... request, journal and error messages, ...
     $request = PKPApplication::getRequest();
     $router = $request->getRouter();
     $journal = $router->getContext($request);
     $error = null;
     // ... search keywords ...
     $query = implode(' ', $searchTerms);
     $keywords = array(null => $query);
     // ... and pagination.
     $rangeInfo = Handler::getRangeInfo($request, 'articlesBySimilarity');
     $rangeInfo->setCount(RECOMMEND_BY_SIMILARITY_PLUGIN_COUNT);
     $results = $articleSearch->retrieveResults($request, $journal, $keywords, $error, null, null, $rangeInfo, array($articleId));
     $smarty->assign('articlesBySimilarity', $results);
     $smarty->assign('articlesBySimilarityQuery', $query);
     $output .= $smarty->fetch($this->getTemplatePath() . 'articleFooter.tpl');
     return false;
 }