path: root/inc/Readability.php

<?php
/** 
* Arc90's Readability ported to PHP for FiveFilters.org
* Based on readability.js version 1.7.1 (without multi-page support)
* Updated to allow HTML5 parsing with html5lib
* Updated with lightClean mode to preserve more images and youtube/vimeo/viddler embeds
* ------------------------------------------------------
* Original URL: http://lab.arc90.com/experiments/readability/js/readability.js
* Arc90's project URL: http://lab.arc90.com/experiments/readability/
* JS Source: http://code.google.com/p/arc90labs-readability
* Ported by: Keyvan Minoukadeh, http://www.keyvan.net
* More information: http://fivefilters.org/content-only/
* License: Apache License, Version 2.0
* Requires: PHP5
* Date: 2012-09-19
* 
* Differences between the PHP port and the original
* ------------------------------------------------------
* Arc90's Readability is designed to run in the browser. It works on the DOM 
* tree (the parsed HTML) after the page's CSS styles have been applied and 
* Javascript code executed. This PHP port does not run inside a browser. 
* We use PHP's ability to parse HTML to build our DOM tree, but we cannot 
* rely on CSS or Javascript support. As such, the results will not always 
* match Arc90's Readability. (For example, if a web page contains CSS style 
* rules or Javascript code which hide certain HTML elements from display, 
* Arc90's Readability will dismiss those from consideration but our PHP port, 
* unable to understand CSS or Javascript, will not know any better.)
* 
* Another significant difference is that the aim of Arc90's Readability is 
* to re-present the main content block of a given web page so users can 
* read it more easily in their browsers. Correct identification, clean up, 
* and separation of the content block is only a part of this process. 
* This PHP port is only concerned with this part, it does not include code 
* that relates to presentation in the browser - Arc90 already do 
* that extremely well, and for PDF output there's FiveFilters.org's 
* PDF Newspaper: http://fivefilters.org/pdf-newspaper/.
* 
* Finally, this class contains methods that might be useful for developers 
* working on HTML document fragments. So without deviating too much from 
* the original code (which I don't want to do because it makes debugging 
* and updating more difficult), I've tried to make it a little more 
* developer friendly. You should be able to use the methods here on 
* existing DOMElement objects without passing an entire HTML document to 
* be parsed.
*/

// This class allows us to do JavaScript like assignements to innerHTML
require_once(dirname(__FILE__).'/JSLikeHTMLElement.php');

// Alternative usage (for testing only!)
// uncomment the lines below and call Readability.php in your browser 
// passing it the URL of the page you'd like content from, e.g.:
// Readability.php?url=http://medialens.org/alerts/09/090615_the_guardian_climate.php

/*
if (!isset($_GET['url']) || $_GET['url'] == '') {
    die('Please pass a URL to the script. E.g. Readability.php?url=bla.com/story.html');
}
$url = $_GET['url'];
if (!preg_match('!^https?://!i', $url)) $url = 'http://'.$url;
$html = file_get_contents($url);
$r = new Readability($html, $url);
$r->init();
echo $r->articleContent->innerHTML;
*/

class Readability
{
    public $version = '1.7.1-without-multi-page';
    public $convertLinksToFootnotes = false;
    public $revertForcedParagraphElements = true;
    public $articleTitle;
    public $articleContent;
    public $dom;
    public $url = null; // optional - URL where HTML was retrieved
    public $debug = false;
    public $lightClean = true; // preserves more content (experimental) added 2012-09-19
    protected $body = null; // 
    protected $bodyCache = null; // Cache the body HTML in case we need to re-use it later
    protected $flags = 7; // 1 | 2 | 4;   // Start with all flags set.
    protected $success = false; // indicates whether we were able to extract or not
    
    /**
    * All of the regular expressions in use within readability.
    * Defined up here so we don't instantiate them repeatedly in loops.
    **/
    public $regexps = array(
        'unlikelyCandidates' => '/combx|comment|community|disqus|extra|foot|header|menu|remark|rss|shoutbox|sidebar|sponsor|ad-break|agegate|pagination|pager|popup/i',
        'okMaybeItsACandidate' => '/and|article|body|column|main|shadow/i',
        'positive' => '/article|body|content|entry|hentry|main|page|attachment|pagination|post|text|blog|story/i',
        'negative' => '/combx|comment|com-|contact|foot|footer|_nav|footnote|masthead|media|meta|outbrain|promo|related|scroll|shoutbox|sidebar|sponsor|shopping|tags|tool|widget/i',
        'divToPElements' => '/<(a|blockquote|dl|div|img|ol|p|pre|table|ul)/i',
        'replaceBrs' => '/(<br[^>]*>[ \n\r\t]*){2,}/i',
        'replaceFonts' => '/<(\/?)font[^>]*>/i',
        // 'trimRe' => '/^\s+|\s+$/g', // PHP has trim()
        'normalize' => '/\s{2,}/',
        'killBreaks' => '/(<br\s*\/?>(\s|&nbsp;?)*){1,}/',
        'video' => '!//(player\.|www\.)?(youtube|vimeo|viddler)\.com!i',
        'skipFootnoteLink' => '/^\s*(\[?[a-z0-9]{1,2}\]?|^|edit|citation needed)\s*$/i'
    );  
    
    /* constants */
    const FLAG_STRIP_UNLIKELYS = 1;
    const FLAG_WEIGHT_CLASSES = 2;
    const FLAG_CLEAN_CONDITIONALLY = 4;
    
    /**
    * Create instance of Readability
    * @param string UTF-8 encoded string
    * @param string (optional) URL associated with HTML (used for footnotes)
    * @param string which parser to use for turning raw HTML into a DOMDocument (either 'libxml' or 'html5lib')
    */  
    function __construct($html, $url=null, $parser='libxml')
    {
        $this->url = $url;
        /* Turn all double br's into p's */
        $html = preg_replace($this->regexps['replaceBrs'], '</p><p>', $html);
        $html = preg_replace($this->regexps['replaceFonts'], '<$1span>', $html);
        $html = mb_convert_encoding($html, 'HTML-ENTITIES', "UTF-8");
        if (trim($html) == '') $html = '<html></html>';
        if ($parser=='html5lib' && ($this->dom = HTML5_Parser::parse($html))) {
            // all good
        } else {
            $this->dom = new DOMDocument();
            $this->dom->preserveWhiteSpace = false;
            @$this->dom->loadHTML($html);
        }
        $this->dom->registerNodeClass('DOMElement', 'JSLikeHTMLElement');
    }

    /**
    * Get article title element
    * @return DOMElement
    */
    public function getTitle() {
        return $this->articleTitle;
    }
    
    /**
    * Get article content element
    * @return DOMElement
    */
    public function getContent() {
        return $this->articleContent;
    }   
    
    /**
    * Runs readability.
    * 
    * Workflow:
    *  1. Prep the document by removing script tags, css, etc.
    *  2. Build readability's DOM tree.
    *  3. Grab the article content from the current dom tree.
    *  4. Replace the current DOM tree with the new one.
    *  5. Read peacefully.
    *
    * @return boolean true if we found content, false otherwise
    **/
    public function init()
    {
        if (!isset($this->dom->documentElement)) return false;
        $this->removeScripts($this->dom);
        //die($this->getInnerHTML($this->dom->documentElement));
        
        // Assume successful outcome
        $this->success = true;

        $bodyElems = $this->dom->getElementsByTagName('body');
        if ($bodyElems->length > 0) {
            if ($this->bodyCache == null) {
                $this->bodyCache = $bodyElems->item(0)->innerHTML;
            }
            if ($this->body == null) {
                $this->body = $bodyElems->item(0);
            }
        }

        $this->prepDocument();
        
        //die($this->dom->documentElement->parentNode->nodeType);
        //$this->setInnerHTML($this->dom->documentElement, $this->getInnerHTML($this->dom->documentElement));
        //die($this->getInnerHTML($this->dom->documentElement));

        /* Build readability's DOM tree */
        $overlay        = $this->dom->createElement('div');
        $innerDiv       = $this->dom->createElement('div');
        $articleTitle   = $this->getArticleTitle();
        $articleContent = $this->grabArticle();

        if (!$articleContent) {
            $this->success = false;
            $articleContent = $this->dom->createElement('div');
            $articleContent->setAttribute('id', 'readability-content');
            $articleContent->innerHTML = '<p>Sorry, Readability was unable to parse this page for content.</p>';        
        }
        
        $overlay->setAttribute('id', 'readOverlay');
        $innerDiv->setAttribute('id', 'readInner');

        /* Glue the structure of our document together. */
        $innerDiv->appendChild($articleTitle);
        $innerDiv->appendChild($articleContent);
        $overlay->appendChild($innerDiv);
        
        /* Clear the old HTML, insert the new content. */
        $this->body->innerHTML = '';
        $this->body->appendChild($overlay);
        //document.body.insertBefore(overlay, document.body.firstChild);
        $this->body->removeAttribute('style');

        $this->postProcessContent($articleContent);
        
        // Set title and content instance variables
        $this->articleTitle = $articleTitle;
        $this->articleContent = $articleContent;
        
        return $this->success;
    }
    
    /**
    * Debug
    */
    protected function dbg($msg) {
        if ($this->debug) echo '* ',$msg, "\n";
    }
    
    /**
    * Run any post-process modifications to article content as necessary.
    *
    * @param DOMElement
    * @return void
    */
    public function postProcessContent($articleContent) {
        if ($this->convertLinksToFootnotes && !preg_match('/wikipedia\.org/', @$this->url)) { 
            $this->addFootnotes($articleContent);
        }
    }
    
    /**
    * Get the article title as an H1.
    *
    * @return DOMElement
    */
    protected function getArticleTitle() {
        $curTitle = '';
        $origTitle = '';

        try {
            $curTitle = $origTitle = $this->getInnerText($this->dom->getElementsByTagName('title')->item(0));
        } catch(Exception $e) {}
        
        if (preg_match('/ [\|\-] /', $curTitle))
        {
            $curTitle = preg_replace('/(.*)[\|\-] .*/i', '$1', $origTitle);
            
            if (count(explode(' ', $curTitle)) < 3) {
                $curTitle = preg_replace('/[^\|\-]*[\|\-](.*)/i', '$1', $origTitle);
            }
        }
        else if (strpos($curTitle, ': ') !== false)
        {
            $curTitle = preg_replace('/.*:(.*)/i', '$1', $origTitle);

            if (count(explode(' ', $curTitle)) < 3) {
                $curTitle = preg_replace('/[^:]*[:](.*)/i','$1', $origTitle);
            }
        }
        else if(strlen($curTitle) > 150 || strlen($curTitle) < 15)
        {
            $hOnes = $this->dom->getElementsByTagName('h1');
            if($hOnes->length == 1)
            {
                $curTitle = $this->getInnerText($hOnes->item(0));
            }
        }

        $curTitle = trim($curTitle);

        if (count(explode(' ', $curTitle)) <= 4) {
            $curTitle = $origTitle;
        }
        
        $articleTitle = $this->dom->createElement('h1');
        $articleTitle->innerHTML = $curTitle;
        
        return $articleTitle;
    }
    
    /**
    * Prepare the HTML document for readability to scrape it.
    * This includes things like stripping javascript, CSS, and handling terrible markup.
    * 
    * @return void
    **/
    protected function prepDocument() {
        /**
        * In some cases a body element can't be found (if the HTML is totally hosed for example)
        * so we create a new body node and append it to the document.
        */
        if ($this->body == null)
        {
            $this->body = $this->dom->createElement('body');
            $this->dom->documentElement->appendChild($this->body);
        }
        $this->body->setAttribute('id', 'readabilityBody');

        /* Remove all style tags in head */
        $styleTags = $this->dom->getElementsByTagName('style');
        for ($i = $styleTags->length-1; $i >= 0; $i--)
        {
            $styleTags->item($i)->parentNode->removeChild($styleTags->item($i));
        }

        /* Turn all double br's into p's */
        /* Note, this is pretty costly as far as processing goes. Maybe optimize later. */
        //document.body.innerHTML = document.body.innerHTML.replace(readability.regexps.replaceBrs, '</p><p>').replace(readability.regexps.replaceFonts, '<$1span>');
        // We do this in the constructor for PHP as that's when we have raw HTML - before parsing it into a DOM tree.
        // Manipulating innerHTML as it's done in JS is not possible in PHP.
    }

    /**
    * For easier reading, convert this document to have footnotes at the bottom rather than inline links.
    * @see http://www.roughtype.com/archives/2010/05/experiments_in.php
    *
    * @return void
    **/
    public function addFootnotes($articleContent) {
        $footnotesWrapper = $this->dom->createElement('div');
        $footnotesWrapper->setAttribute('id', 'readability-footnotes');
        $footnotesWrapper->innerHTML = '<h3>References</h3>';
        
        $articleFootnotes = $this->dom->createElement('ol');
        $articleFootnotes->setAttribute('id', 'readability-footnotes-list');
        $footnotesWrapper->appendChild($articleFootnotes);
        
        $articleLinks = $articleContent->getElementsByTagName('a');
        
        $linkCount = 0;
        for ($i = 0; $i < $articleLinks->length; $i++)
        {
            $articleLink  = $articleLinks->item($i);
            $footnoteLink = $articleLink->cloneNode(true);
            $refLink      = $this->dom->createElement('a');
            $footnote     = $this->dom->createElement('li');
            $linkDomain   = @parse_url($footnoteLink->getAttribute('href'), PHP_URL_HOST);
            if (!$linkDomain && isset($this->url)) $linkDomain = @parse_url($this->url, PHP_URL_HOST);
            //linkDomain   = footnoteLink.host ? footnoteLink.host : document.location.host,
            $linkText     = $this->getInnerText($articleLink);
            
            if ((strpos($articleLink->getAttribute('class'), 'readability-DoNotFootnote') !== false) || preg_match($this->regexps['skipFootnoteLink'], $linkText)) {
                continue;
            }
            
            $linkCount++;

            /** Add a superscript reference after the article link */
            $refLink->setAttribute('href', '#readabilityFootnoteLink-' . $linkCount);
            $refLink->innerHTML = '<small><sup>[' . $linkCount . ']</sup></small>';
            $refLink->setAttribute('class', 'readability-DoNotFootnote');
            $refLink->setAttribute('style', 'color: inherit;');
            
            //TODO: does this work or should we use DOMNode.isSameNode()?
            if ($articleLink->parentNode->lastChild == $articleLink) {
                $articleLink->parentNode->appendChild($refLink);
            } else {
                $articleLink->parentNode->insertBefore($refLink, $articleLink->nextSibling);
            }

            $articleLink->setAttribute('style', 'color: inherit; text-decoration: none;');
            $articleLink->setAttribute('name', 'readabilityLink-' . $linkCount);

            $footnote->innerHTML = '<small><sup><a href="#readabilityLink-' . $linkCount . '" title="Jump to Link in Article">^</a></sup></small> ';

            $footnoteLink->innerHTML = ($footnoteLink->getAttribute('title') != '' ? $footnoteLink->getAttribute('title') : $linkText);
            $footnoteLink->setAttribute('name', 'readabilityFootnoteLink-' . $linkCount);
            
            $footnote->appendChild($footnoteLink);
            if ($linkDomain) $footnote->innerHTML = $footnote->innerHTML . '<small> (' . $linkDomain . ')</small>';
            
            $articleFootnotes->appendChild($footnote);
        }

        if ($linkCount > 0) {
            $articleContent->appendChild($footnotesWrapper);           
        }
    }

    /**
    * Reverts P elements with class 'readability-styled'
    * to text nodes - which is what they were before.
    *
    * @param DOMElement
    * @return void
    */
    function revertReadabilityStyledElements($articleContent) {
        $xpath = new DOMXPath($articleContent->ownerDocument);
        $elems = $xpath->query('.//p[@class="readability-styled"]', $articleContent);
        //$elems = $articleContent->getElementsByTagName('p');
        for ($i = $elems->length-1; $i >= 0; $i--) {
            $e = $elems->item($i);
            $e->parentNode->replaceChild($articleContent->ownerDocument->createTextNode($e->textContent), $e);
            //if ($e->hasAttribute('class') && $e->getAttribute('class') == 'readability-styled') {
            //  $e->parentNode->replaceChild($this->dom->createTextNode($e->textContent), $e);
            //}
        }
    }
    
    /**
    * Prepare the article node for display. Clean out any inline styles,
    * iframes, forms, strip extraneous <p> tags, etc.
    *
    * @param DOMElement
    * @return void
    */
    function prepArticle($articleContent) {
        $this->cleanStyles($articleContent);
        $this->killBreaks($articleContent);
        if ($this->revertForcedParagraphElements) {
            $this->revertReadabilityStyledElements($articleContent);
        }

        /* Clean out junk from the article content */
        $this->cleanConditionally($articleContent, 'form');
        $this->clean($articleContent, 'object');
        $this->clean($articleContent, 'h1');

        /**
        * If there is only one h2, they are probably using it
        * as a header and not a subheader, so remove it since we already have a header.
        ***/
        if (!$this->lightClean && ($articleContent->getElementsByTagName('h2')->length == 1)) {
            $this->clean($articleContent, 'h2'); 
        }
        $this->clean($articleContent, 'iframe');

        $this->cleanHeaders($articleContent);

        /* Do these last as the previous stuff may have removed junk that will affect these */
        $this->cleanConditionally($articleContent, 'table');
        $this->cleanConditionally($articleContent, 'ul');
        $this->cleanConditionally($articleContent, 'div');

        /* Remove extra paragraphs */
        $articleParagraphs = $articleContent->getElementsByTagName('p');
        for ($i = $articleParagraphs->length-1; $i >= 0; $i--)
        {
            $imgCount    = $articleParagraphs->item($i)->getElementsByTagName('img')->length;
            $embedCount  = $articleParagraphs->item($i)->getElementsByTagName('embed')->length;
            $objectCount = $articleParagraphs->item($i)->getElementsByTagName('object')->length;
            $iframeCount = $articleParagraphs->item($i)->getElementsByTagName('iframe')->length;
            
            if ($imgCount === 0 && $embedCount === 0 && $objectCount === 0 && $iframeCount === 0 && $this->getInnerText($articleParagraphs->item($i), false) == '')
            {
                $articleParagraphs->item($i)->parentNode->removeChild($articleParagraphs->item($i));
            }
        }

        try {
            $articleContent->innerHTML = preg_replace('/<br[^>]*>\s*<p/i', '<p', $articleContent->innerHTML);
            //articleContent.innerHTML = articleContent.innerHTML.replace(/<br[^>]*>\s*<p/gi, '<p');      
        }
        catch (Exception $e) {
            $this->dbg("Cleaning innerHTML of breaks failed. This is an IE strict-block-elements bug. Ignoring.: " . $e);
        }
    }
    
    /**
    * Initialize a node with the readability object. Also checks the
    * className/id for special names to add to its score.
    *
    * @param Element
    * @return void
    **/
    protected function initializeNode($node) {
        $readability = $this->dom->createAttribute('readability');
        $readability->value = 0; // this is our contentScore
        $node->setAttributeNode($readability);               

        switch (strtoupper($node->tagName)) { // unsure if strtoupper is needed, but using it just in case
            case 'DIV':
                $readability->value += 5;
                break;

            case 'PRE':
            case 'TD':
            case 'BLOCKQUOTE':
                $readability->value += 3;
                break;
                
            case 'ADDRESS':
            case 'OL':
            case 'UL':
            case 'DL':
            case 'DD':
            case 'DT':
            case 'LI':
            case 'FORM':
                $readability->value -= 3;
                break;

            case 'H1':
            case 'H2':
            case 'H3':
            case 'H4':
            case 'H5':
            case 'H6':
            case 'TH':
                $readability->value -= 5;
                break;
        }
        $readability->value += $this->getClassWeight($node);
    }
    
    /***
    * grabArticle - Using a variety of metrics (content score, classname, element types), find the content that is
    *               most likely to be the stuff a user wants to read. Then return it wrapped up in a div.
    *
    * @return DOMElement
    **/
    protected function grabArticle($page=null) {
        $stripUnlikelyCandidates = $this->flagIsActive(self::FLAG_STRIP_UNLIKELYS);
        if (!$page) $page = $this->dom;
        $allElements = $page->getElementsByTagName('*');
        /**
        * First, node prepping. Trash nodes that look cruddy (like ones with the class name "comment", etc), and turn divs
        * into P tags where they have been used inappropriately (as in, where they contain no other block level elements.)
        *
        * Note: Assignment from index for performance. See http://www.peachpit.com/articles/article.aspx?p=31567&seqNum=5
        * TODO: Shouldn't this be a reverse traversal?
        **/
        $node = null;
        $nodesToScore = array();
        for ($nodeIndex = 0; ($node = $allElements->item($nodeIndex)); $nodeIndex++) {
        //for ($nodeIndex=$targetList->length-1; $nodeIndex >= 0; $nodeIndex--) {
            //$node = $targetList->item($nodeIndex);
            $tagName = strtoupper($node->tagName);
            /* Remove unlikely candidates */
            if ($stripUnlikelyCandidates) {
                $unlikelyMatchString = $node->getAttribute('class') . $node->getAttribute('id');
                if (
                    preg_match($this->regexps['unlikelyCandidates'], $unlikelyMatchString) &&
                    !preg_match($this->regexps['okMaybeItsACandidate'], $unlikelyMatchString) &&
                    $tagName != 'BODY'
                )
                {
                    $this->dbg('Removing unlikely candidate - ' . $unlikelyMatchString);
                    //$nodesToRemove[] = $node;
                    $node->parentNode->removeChild($node);
                    $nodeIndex--;
                    continue;
                }               
            }

            if ($tagName == 'P' || $tagName == 'TD' || $tagName == 'PRE') {
                $nodesToScore[] = $node;
            }

            /* Turn all divs that don't have children block level elements into p's */
            if ($tagName == 'DIV') {
                if (!preg_match($this->regexps['divToPElements'], $node->innerHTML)) {
                    //$this->dbg('Altering div to p');
                    $newNode = $this->dom->createElement('p');
                    try {
                        $newNode->innerHTML = $node->innerHTML;
                        //$nodesToReplace[] = array('new'=>$newNode, 'old'=>$node);
                        $node->parentNode->replaceChild($newNode, $node);
                        $nodeIndex--;
                        $nodesToScore[] = $node; // or $newNode?
                    }
                    catch(Exception $e) {
                        $this->dbg('Could not alter div to p, reverting back to div.: ' . $e);
                    }
                }
                else
                {
                    /* EXPERIMENTAL */
                    // TODO: change these p elements back to text nodes after processing
                    for ($i = 0, $il = $node->childNodes->length; $i < $il; $i++) {
                        $childNode = $node->childNodes->item($i);
                        if ($childNode->nodeType == 3) { // XML_TEXT_NODE
                            //$this->dbg('replacing text node with a p tag with the same content.');
                            $p = $this->dom->createElement('p');
                            $p->innerHTML = $childNode->nodeValue;
                            $p->setAttribute('style', 'display: inline;');
                            $p->setAttribute('class', 'readability-styled');
                            $childNode->parentNode->replaceChild($p, $childNode);
                        }
                    }
                }
            }
        }
        
        /**
        * Loop through all paragraphs, and assign a score to them based on how content-y they look.
        * Then add their score to their parent node.
        *
        * A score is determined by things like number of commas, class names, etc. Maybe eventually link density.
        **/
        $candidates = array();
        for ($pt=0; $pt < count($nodesToScore); $pt++) {
            $parentNode      = $nodesToScore[$pt]->parentNode;
            // $grandParentNode = $parentNode ? $parentNode->parentNode : null;
            $grandParentNode = !$parentNode ? null : (($parentNode->parentNode instanceof DOMElement) ? $parentNode->parentNode : null);
            $innerText       = $this->getInnerText($nodesToScore[$pt]);

            if (!$parentNode || !isset($parentNode->tagName)) {
                continue;
            }

            /* If this paragraph is less than 25 characters, don't even count it. */
            if(strlen($innerText) < 25) {
                continue;
            }

            /* Initialize readability data for the parent. */
            if (!$parentNode->hasAttribute('readability')) 
            {
                $this->initializeNode($parentNode);
                $candidates[] = $parentNode;
            }

            /* Initialize readability data for the grandparent. */
            if ($grandParentNode && !$grandParentNode->hasAttribute('readability') && isset($grandParentNode->tagName))
            {
                $this->initializeNode($grandParentNode);
                $candidates[] = $grandParentNode;
            }

            $contentScore = 0;

            /* Add a point for the paragraph itself as a base. */
            $contentScore++;

            /* Add points for any commas within this paragraph */
            $contentScore += count(explode(',', $innerText));
            
            /* For every 100 characters in this paragraph, add another point. Up to 3 points. */
            $contentScore += min(floor(strlen($innerText) / 100), 3);
            
            /* Add the score to the parent. The grandparent gets half. */
            $parentNode->getAttributeNode('readability')->value += $contentScore;

            if ($grandParentNode) {
                $grandParentNode->getAttributeNode('readability')->value += $contentScore/2;             
            }
        }

        /**
        * After we've calculated scores, loop through all of the possible candidate nodes we found
        * and find the one with the highest score.
        **/
        $topCandidate = null;
        for ($c=0, $cl=count($candidates); $c < $cl; $c++)
        {
            /**
            * Scale the final candidates score based on link density. Good content should have a
            * relatively small link density (5% or less) and be mostly unaffected by this operation.
            **/
            $readability = $candidates[$c]->getAttributeNode('readability');
            $readability->value = $readability->value * (1-$this->getLinkDensity($candidates[$c]));

            $this->dbg('Candidate: ' . $candidates[$c]->tagName . ' (' . $candidates[$c]->getAttribute('class') . ':' . $candidates[$c]->getAttribute('id') . ') with score ' . $readability->value);

            if (!$topCandidate || $readability->value > (int)$topCandidate->getAttribute('readability')) {
                $topCandidate = $candidates[$c];
            }
        }

        /**
        * If we still have no top candidate, just use the body as a last resort.
        * We also have to copy the body node so it is something we can modify.
        **/
        if ($topCandidate === null || strtoupper($topCandidate->tagName) == 'BODY')
        {
            $topCandidate = $this->dom->createElement('div');
            if ($page instanceof DOMDocument) {
                if (!isset($page->documentElement)) {
                    // we don't have a body either? what a mess! :)
                } else {
                    $topCandidate->innerHTML = $page->documentElement->innerHTML;
                    $page->documentElement->innerHTML = '';
                    $page->documentElement->appendChild($topCandidate);
                }
            } else {
                $topCandidate->innerHTML = $page->innerHTML;
                $page->innerHTML = '';
                $page->appendChild($topCandidate);
            }
            $this->initializeNode($topCandidate);
        }

        /**
        * Now that we have the top candidate, look through its siblings for content that might also be related.
        * Things like preambles, content split by ads that we removed, etc.
        **/
        $articleContent        = $this->dom->createElement('div');
        $articleContent->setAttribute('id', 'readability-content');
        $siblingScoreThreshold = max(10, ((int)$topCandidate->getAttribute('readability')) * 0.2);
        $siblingNodes          = $topCandidate->parentNode->childNodes;
        if (!isset($siblingNodes)) {
            $siblingNodes = new stdClass;
            $siblingNodes->length = 0;
        }

        for ($s=0, $sl=$siblingNodes->length; $s < $sl; $s++)
        {
            $siblingNode = $siblingNodes->item($s);
            $append      = false;

            $this->dbg('Looking at sibling node: ' . $siblingNode->nodeName . (($siblingNode->nodeType === XML_ELEMENT_NODE && $siblingNode->hasAttribute('readability')) ? (' with score ' . $siblingNode->getAttribute('readability')) : ''));

            //dbg('Sibling has score ' . ($siblingNode->readability ? siblingNode.readability.contentScore : 'Unknown'));

            if ($siblingNode === $topCandidate)
            // or if ($siblingNode->isSameNode($topCandidate))
            {
                $append = true;
            }

            $contentBonus = 0;
            /* Give a bonus if sibling nodes and top candidates have the example same classname */
            if ($siblingNode->nodeType === XML_ELEMENT_NODE && $siblingNode->getAttribute('class') == $topCandidate->getAttribute('class') && $topCandidate->getAttribute('class') != '') {
                $contentBonus += ((int)$topCandidate->getAttribute('readability')) * 0.2;
            }

            if ($siblingNode->nodeType === XML_ELEMENT_NODE && $siblingNode->hasAttribute('readability') && (((int)$siblingNode->getAttribute('readability')) + $contentBonus) >= $siblingScoreThreshold)
            {
                $append = true;
            }
            
            if (strtoupper($siblingNode->nodeName) == 'P') {
                $linkDensity = $this->getLinkDensity($siblingNode);
                $nodeContent = $this->getInnerText($siblingNode);
                $nodeLength  = strlen($nodeContent);
                
                if ($nodeLength > 80 && $linkDensity < 0.25)
                {
                    $append = true;
                }
                else if ($nodeLength < 80 && $linkDensity === 0 && preg_match('/\.( |$)/', $nodeContent))
                {
                    $append = true;
                }
            }

            if ($append)
            {
                $this->dbg('Appending node: ' . $siblingNode->nodeName);

                $nodeToAppend = null;
                $sibNodeName = strtoupper($siblingNode->nodeName);
                if ($sibNodeName != 'DIV' && $sibNodeName != 'P') {
                    /* We have a node that isn't a common block level element, like a form or td tag. Turn it into a div so it doesn't get filtered out later by accident. */
                    
                    $this->dbg('Altering siblingNode of ' . $sibNodeName . ' to div.');
                    $nodeToAppend = $this->dom->createElement('div');
                    try {
                        $nodeToAppend->setAttribute('id', $siblingNode->getAttribute('id'));
                        $nodeToAppend->innerHTML = $siblingNode->innerHTML;
                    }
                    catch(Exception $e)
                    {
                        $this->dbg('Could not alter siblingNode to div, reverting back to original.');
                        $nodeToAppend = $siblingNode;
                        $s--;
                        $sl--;
                    }
                } else {
                    $nodeToAppend = $siblingNode;
                    $s--;
                    $sl--;
                }
                
                /* To ensure a node does not interfere with readability styles, remove its classnames */
                $nodeToAppend->removeAttribute('class');

                /* Append sibling and subtract from our list because it removes the node when you append to another node */
                $articleContent->appendChild($nodeToAppend);
            }
        }

        /**
        * So we have all of the content that we need. Now we clean it up for presentation.
        **/
        $this->prepArticle($articleContent);

        /**
        * Now that we've gone through the full algorithm, check to see if we got any meaningful content.
        * If we didn't, we may need to re-run grabArticle with different flags set. This gives us a higher
        * likelihood of finding the content, and the sieve approach gives us a higher likelihood of
        * finding the -right- content.
        **/
        if (strlen($this->getInnerText($articleContent, false)) < 250)
        {
            // TODO: find out why element disappears sometimes, e.g. for this URL http://www.businessinsider.com/6-hedge-fund-etfs-for-average-investors-2011-7
            // in the meantime, we check and create an empty element if it's not there.
            if (!isset($this->body->childNodes)) $this->body = $this->dom->createElement('body');
            $this->body->innerHTML = $this->bodyCache;
            
            if ($this->flagIsActive(self::FLAG_STRIP_UNLIKELYS)) {
                $this->removeFlag(self::FLAG_STRIP_UNLIKELYS);
                return $this->grabArticle($this->body);
            }
            else if ($this->flagIsActive(self::FLAG_WEIGHT_CLASSES)) {
                $this->removeFlag(self::FLAG_WEIGHT_CLASSES);
                return $this->grabArticle($this->body);              
            }
            else if ($this->flagIsActive(self::FLAG_CLEAN_CONDITIONALLY)) {
                $this->removeFlag(self::FLAG_CLEAN_CONDITIONALLY);
                return $this->grabArticle($this->body);
            }
            else {
                return false;
            }
        }
        return $articleContent;
    }
    
    /**
    * Remove script tags from document
    *
    * @param DOMElement
    * @return void
    */
    public function removeScripts($doc) {
        $scripts = $doc->getElementsByTagName('script');
        for($i = $scripts->length-1; $i >= 0; $i--)
        {
            $scripts->item($i)->parentNode->removeChild($scripts->item($i));
        }
    }
    
    /**
    * Get the inner text of a node.
    * This also strips out any excess whitespace to be found.
    *
    * @param DOMElement $
    * @param boolean $normalizeSpaces (default: true)
    * @return string
    **/
    public function getInnerText($e, $normalizeSpaces=true) {
        $textContent = '';

        if (!isset($e->textContent) || $e->textContent == '') {
            return '';
        }

        $textContent = trim($e->textContent);

        if ($normalizeSpaces) {
            return preg_replace($this->regexps['normalize'], ' ', $textContent);
        } else {
            return $textContent;
        }
    }

    /**
    * Get the number of times a string $s appears in the node $e.
    *
    * @param DOMElement $e
    * @param string - what to count. Default is ","
    * @return number (integer)
    **/
    public function getCharCount($e, $s=',') {
        return substr_count($this->getInnerText($e), $s);
    }

    /**
    * Remove the style attribute on every $e and under.
    *
    * @param DOMElement $e
    * @return void
    */
    public function cleanStyles($e) {
        if (!is_object($e)) return;
        $elems = $e->getElementsByTagName('*');
        foreach ($elems as $elem) {
            $elem->removeAttribute('style');
        }
    }
    
    /**
    * Get the density of links as a percentage of the content
    * This is the amount of text that is inside a link divided by the total text in the node.
    * 
    * @param DOMElement $e
    * @return number (float)
    */
    public function getLinkDensity($e) {
        $links      = $e->getElementsByTagName('a');
        $textLength = strlen($this->getInnerText($e));
        $linkLength = 0;
        for ($i=0, $il=$links->length; $i < $il; $i++)
        {
            $linkLength += strlen($this->getInnerText($links->item($i)));
        }
        if ($textLength > 0) {
            return $linkLength / $textLength;
        } else {
            return 0;
        }
    }
    
    /**
    * Get an elements class/id weight. Uses regular expressions to tell if this 
    * element looks good or bad.
    *
    * @param DOMElement $e
    * @return number (Integer)
    */
    public function getClassWeight($e) {
        if(!$this->flagIsActive(self::FLAG_WEIGHT_CLASSES)) {
            return 0;
        }

        $weight = 0;

        /* Look for a special classname */
        if ($e->hasAttribute('class') && $e->getAttribute('class') != '')
        {
            if (preg_match($this->regexps['negative'], $e->getAttribute('class'))) {
                $weight -= 25;
            }
            if (preg_match($this->regexps['positive'], $e->getAttribute('class'))) {
                $weight += 25;
            }
        }

        /* Look for a special ID */
        if ($e->hasAttribute('id') && $e->getAttribute('id') != '')
        {
            if (preg_match($this->regexps['negative'], $e->getAttribute('id'))) {
                $weight -= 25;
            }
            if (preg_match($this->regexps['positive'], $e->getAttribute('id'))) {
                $weight += 25;
            }
        }
        return $weight;
    }

    /**
    * Remove extraneous break tags from a node.
    *
    * @param DOMElement $node
    * @return void
    */
    public function killBreaks($node) {
        $html = $node->innerHTML;
        $html = preg_replace($this->regexps['killBreaks'], '<br />', $html);
        $node->innerHTML = $html;
    }

    /**
    * Clean a node of all elements of type "tag".
    * (Unless it's a youtube/vimeo video. People love movies.)
    *
    * Updated 2012-09-18 to preserve youtube/vimeo iframes
    *
    * @param DOMElement $e
    * @param string $tag
    * @return void
    */
    public function clean($e, $tag) {
        $targetList = $e->getElementsByTagName($tag);
        $isEmbed = ($tag == 'iframe' || $tag == 'object' || $tag == 'embed');
        
        for ($y=$targetList->length-1; $y >= 0; $y--) {
            /* Allow youtube and vimeo videos through as people usually want to see those. */
            if ($isEmbed) {
                $attributeValues = '';
                for ($i=0, $il=$targetList->item($y)->attributes->length; $i < $il; $i++) {
                    $attributeValues .= $targetList->item($y)->attributes->item($i)->value . '|'; // DOMAttr? (TODO: test)
                }
                
                /* First, check the elements attributes to see if any of them contain youtube or vimeo */
                if (preg_match($this->regexps['video'], $attributeValues)) {
                    continue;
                }

                /* Then check the elements inside this element for the same. */
                if (preg_match($this->regexps['video'], $targetList->item($y)->innerHTML)) {
                    continue;
                }
            }
            $targetList->item($y)->parentNode->removeChild($targetList->item($y));
        }
    }
    
    /**
    * Clean an element of all tags of type "tag" if they look fishy.
    * "Fishy" is an algorithm based on content length, classnames, 
    * link density, number of images & embeds, etc.
    *
    * @param DOMElement $e
    * @param string $tag
    * @return void
    */
    public function cleanConditionally($e, $tag) {
        if (!$this->flagIsActive(self::FLAG_CLEAN_CONDITIONALLY)) {
            return;
        }

        $tagsList = $e->getElementsByTagName($tag);
        $curTagsLength = $tagsList->length;

        /**
        * Gather counts for other typical elements embedded within.
        * Traverse backwards so we can remove nodes at the same time without effecting the traversal.
        *
        * TODO: Consider taking into account original contentScore here.
        */
        for ($i=$curTagsLength-1; $i >= 0; $i--) {
            $weight = $this->getClassWeight($tagsList->item($i));
            $contentScore = ($tagsList->item($i)->hasAttribute('readability')) ? (int)$tagsList->item($i)->getAttribute('readability') : 0;
            
            $this->dbg('Cleaning Conditionally ' . $tagsList->item($i)->tagName . ' (' . $tagsList->item($i)->getAttribute('class') . ':' . $tagsList->item($i)->getAttribute('id') . ')' . (($tagsList->item($i)->hasAttribute('readability')) ? (' with score ' . $tagsList->item($i)->getAttribute('readability')) : ''));

            if ($weight + $contentScore < 0) {
                $tagsList->item($i)->parentNode->removeChild($tagsList->item($i));
            }
            else if ( $this->getCharCount($tagsList->item($i), ',') < 10) {
                /**
                * If there are not very many commas, and the number of
                * non-paragraph elements is more than paragraphs or other ominous signs, remove the element.
                **/
                $p      = $tagsList->item($i)->getElementsByTagName('p')->length;
                $img    = $tagsList->item($i)->getElementsByTagName('img')->length;
                $li     = $tagsList->item($i)->getElementsByTagName('li')->length-100;
                $input  = $tagsList->item($i)->getElementsByTagName('input')->length;
                $a      = $tagsList->item($i)->getElementsByTagName('a')->length;

                $embedCount = 0;
                $embeds = $tagsList->item($i)->getElementsByTagName('embed');
                for ($ei=0, $il=$embeds->length; $ei < $il; $ei++) {
                    if (preg_match($this->regexps['video'], $embeds->item($ei)->getAttribute('src'))) {
                        $embedCount++; 
                    }
                }
                $embeds = $tagsList->item($i)->getElementsByTagName('iframe');
                for ($ei=0, $il=$embeds->length; $ei < $il; $ei++) {
                    if (preg_match($this->regexps['video'], $embeds->item($ei)->getAttribute('src'))) {
                        $embedCount++; 
                    }
                }

                $linkDensity   = $this->getLinkDensity($tagsList->item($i));
                $contentLength = strlen($this->getInnerText($tagsList->item($i)));
                $toRemove      = false;

                if ($this->lightClean) {
                    $this->dbg('Light clean...');
                    if ( ($img > $p) && ($img > 4) ) {
                        $this->dbg(' more than 4 images and more image elements than paragraph elements');
                        $toRemove = true;
                    } else if ($li > $p && $tag != 'ul' && $tag != 'ol') {
                        $this->dbg(' too many <li> elements, and parent is not <ul> or <ol>');
                        $toRemove = true;
                    } else if ( $input > floor($p/3) ) {
                        $this->dbg(' too many <input> elements');
                        $toRemove = true; 
                    } else if ($contentLength < 25 && ($embedCount === 0 && ($img === 0 || $img > 2))) {
                        $this->dbg(' content length less than 25 chars, 0 embeds and either 0 images or more than 2 images');
                        $toRemove = true;
                    } else if($weight < 25 && $linkDensity > 0.2) {
                        $this->dbg(' weight smaller than 25 and link density above 0.2');
                        $toRemove = true;
                    } else if($a > 2 && ($weight >= 25 && $linkDensity > 0.5)) {
                        $this->dbg(' more than 2 links and weight above 25 but link density greater than 0.5');
                        $toRemove = true;
                    } else if($embedCount > 3) {
                        $this->dbg(' more than 3 embeds');
                        $toRemove = true;
                    }
                } else {
                    $this->dbg('Standard clean...');
                    if ( $img > $p ) {
                        $this->dbg(' more image elements than paragraph elements');
                        $toRemove = true;
                    } else if ($li > $p && $tag != 'ul' && $tag != 'ol') {
                        $this->dbg(' too many <li> elements, and parent is not <ul> or <ol>');
                        $toRemove = true;
                    } else if ( $input > floor($p/3) ) {
                        $this->dbg(' too many <input> elements');
                        $toRemove = true; 
                    } else if ($contentLength < 25 && ($img === 0 || $img > 2) ) {
                        $this->dbg(' content length less than 25 chars and 0 images, or more than 2 images');
                        $toRemove = true;
                    } else if($weight < 25 && $linkDensity > 0.2) {
                        $this->dbg(' weight smaller than 25 and link density above 0.2');
                        $toRemove = true;
                    } else if($weight >= 25 && $linkDensity > 0.5) {
                        $this->dbg(' weight above 25 but link density greater than 0.5');
                        $toRemove = true;
                    } else if(($embedCount == 1 && $contentLength < 75) || $embedCount > 1) {
                        $this->dbg(' 1 embed and content length smaller than 75 chars, or more than one embed');
                        $toRemove = true;
                    }
                }

                if ($toRemove) {
                    //$this->dbg('Removing: '.$tagsList->item($i)->innerHTML);
                    $tagsList->item($i)->parentNode->removeChild($tagsList->item($i));
                }
            }
        }
    }

    /**
    * Clean out spurious headers from an Element. Checks things like classnames and link density.
    *
    * @param DOMElement $e
    * @return void
    */
    public function cleanHeaders($e) {
        for ($headerIndex = 1; $headerIndex < 3; $headerIndex++) {
            $headers = $e->getElementsByTagName('h' . $headerIndex);
            for ($i=$headers->length-1; $i >=0; $i--) {
                if ($this->getClassWeight($headers->item($i)) < 0 || $this->getLinkDensity($headers->item($i)) > 0.33) {
                    $headers->item($i)->parentNode->removeChild($headers->item($i));
                }
            }
        }
    }

    public function flagIsActive($flag) {
        return ($this->flags & $flag) > 0;
    }
    
    public function addFlag($flag) {
        $this->flags = $this->flags | $flag;
    }
    
    public function removeFlag($flag) {
        $this->flags = $this->flags & ~$flag;
    }
}