Stream filter to convert HTML5 to XML

HTMLToXMLFilter.php

<?php

/**
 * Stream filter to convert HTML5 to XML.
 * 
 * <code>
 *   $dsn = "php://filter/read=htmltoxml/resource=" . $url;
 *   $xml = XMLReader::open($dsn);
 * </code>
 * 
 * @todo Fix partial tag in bucket
 */
class HTMLToXMLFilter extends php_user_filter
{
    /** Decode HTML entities */
    const ENTITIES = 1;
    
    /** Self close elements */
    const SELFCLOSE = 2;
    
    
    /**
     * XML entity list
     * @var array
     */
    public static $entitylist = array(
        '"' => '&quot;',
        '&' => '&amp;',
        '<' => '&lt;',
        '>' => '&gt;',
    );

    /**
     * HTML elements that should self close
     * @var array
     */
    public static $closeTags = array(
        'area',
        'base',
        'br',
        'col',
        'command',
        'embed',
        'hr',
        'img',
        'input',
        'keygen',
        'link',
        'meta',
        'param',
        'source',
        'track',
        'wbr'
    );
    
    
    /**
     * @var int
     */
    protected $mode;
    

    /**
     * Called when the filter is created
     * 
     * @return boolean
     */
    public function onCreate()
    {
        switch ($this->filtername) {
            case 'htmltoxml':
                $this->mode = self::ENTITIES | self::SELFCLOSE;
                break;
            
            case 'htmltoxml.entities':
                $this->mode = self::ENTITIES;
                break;
            
            case 'htmltoxml.selfclose':
                $this->mode = self::SELFCLOSE;
                break;
            
            default:
                return false;
        }

        return true;
    }

    /**
     * Filter function
     * 
     * @param resource $in
     * @param resource $out
     * @param int      $consumed
     * @param bool     $closing
     * @return string
     */
    public function filter($in, $out, &$consumed, $closing)
    {
        while ($bucket = stream_bucket_make_writeable($in)) {
            $data = $bucket->data;
            
            // Decode HTML entites
            if ($this->mode & self::ENTITIES) {
                $data = preg_replace_callback('/&(?:\w+;)?/', array($this, 'decode'), $data);
            }
            
            // Self close HTML elements
            if ($this->mode & self::SELFCLOSE) {
                $close_regex = '~<' . join('|', static::$closeTags) . '\s[^>]++(?<!/)>~';
                $data = preg_replace_callback($close_regex, array($this, 'selfClose'), $data);
            }
            
            $bucket->data = $data;
            $consumed += $bucket->datalen;
            stream_bucket_append($out, $bucket);
        }
        
        return PSFS_PASS_ON;
    }
    
    /**
     * Replace callback to decode HTML entities
     * 
     * @param array $matches
     * @return string
     */
    public function decode($matches)
    {
        list($entity) = $matches;
        
        if ($entity === '&') return '&amp;';
        if (in_array($entity, static::$entitylist)) return $entity;
        
        return html_entity_decode($entity);
    }
    
    /**
     * Self close element
     * 
     * @param array $matches
     * @return string
     */
    public function selfClose($matches)
    {
        return substr($matches[0], 0, -1) . '/>';
    }
}

stream_filter_register("htmltoxml", "HTMLToXMLFilter");
stream_filter_register("htmltoxml.*", "HTMLToXMLFilter");