HTMLPurifier_Encoder::convertToUTF8 PHP Method

    public static function convertToUTF8($str, $config, $context)
    {
        $encoding = $config->get('Core.Encoding');
        if ($encoding === 'utf-8') {
            return $str;
        }
        static $iconv = null;
        if ($iconv === null) {
            $iconv = self::iconvAvailable();
        }
        if ($iconv && !$config->get('Test.ForceNoIconv')) {
            // unaffected by bugs, since UTF-8 support all characters
            $str = self::unsafeIconv($encoding, 'utf-8//IGNORE', $str);
            if ($str === false) {
                // $encoding is not a valid encoding
                trigger_error('Invalid encoding ' . $encoding, E_USER_ERROR);
                return '';
            }
            // If the string is bjorked by Shift_JIS or a similar encoding
            // that doesn't support all of ASCII, convert the naughty
            // characters to their true byte-wise ASCII/UTF-8 equivalents.
            $str = strtr($str, self::testEncodingSupportsASCII($encoding));
            return $str;
        } elseif ($encoding === 'iso-8859-1') {
            $str = utf8_encode($str);
            return $str;
        }
        $bug = HTMLPurifier_Encoder::testIconvTruncateBug();
        if ($bug == self::ICONV_OK) {
            trigger_error('Encoding not supported, please install iconv', E_USER_ERROR);
        } else {
            trigger_error('You have a buggy version of iconv, see https://bugs.php.net/bug.php?id=48147 ' . 'and http://sourceware.org/bugzilla/show_bug.cgi?id=13541', E_USER_ERROR);
        }
    }

 /**
  * Filters an HTML snippet/document to be XSS-free and standards-compliant.
  *
  * @param $html String of HTML to purify
  * @param $config HTMLPurifier_Config object for this operation, if omitted,
  *                defaults to the config object specified during this
  *                object's construction. The parameter can also be any type
  *                that HTMLPurifier_Config::create() supports.
  * @return Purified HTML
  */
 public function purify($html, $config = null)
 {
     // :TODO: make the config merge in, instead of replace
     $config = $config ? HTMLPurifier_Config::create($config) : $this->config;
     // implementation is partially environment dependant, partially
     // configuration dependant
     $lexer = HTMLPurifier_Lexer::create($config);
     $context = new HTMLPurifier_Context();
     // setup HTML generator
     $this->generator = new HTMLPurifier_Generator($config, $context);
     $context->register('Generator', $this->generator);
     // set up global context variables
     if ($config->get('Core.CollectErrors')) {
         // may get moved out if other facilities use it
         $language_factory = HTMLPurifier_LanguageFactory::instance();
         $language = $language_factory->create($config, $context);
         $context->register('Locale', $language);
         $error_collector = new HTMLPurifier_ErrorCollector($context);
         $context->register('ErrorCollector', $error_collector);
     }
     // setup id_accumulator context, necessary due to the fact that
     // AttrValidator can be called from many places
     $id_accumulator = HTMLPurifier_IDAccumulator::build($config, $context);
     $context->register('IDAccumulator', $id_accumulator);
     $html = HTMLPurifier_Encoder::convertToUTF8($html, $config, $context);
     // setup filters
     $filter_flags = $config->getBatch('Filter');
     $custom_filters = $filter_flags['Custom'];
     unset($filter_flags['Custom']);
     $filters = array();
     foreach ($filter_flags as $filter => $flag) {
         if (!$flag) {
             continue;
         }
         if (strpos($filter, '.') !== false) {
             continue;
         }
         $class = "HTMLPurifier_Filter_{$filter}";
         $filters[] = new $class();
     }
     foreach ($custom_filters as $filter) {
         // maybe "HTMLPurifier_Filter_$filter", but be consistent with AutoFormat
         $filters[] = $filter;
     }
     $filters = array_merge($filters, $this->filters);
     // maybe prepare(), but later
     for ($i = 0, $filter_size = count($filters); $i < $filter_size; $i++) {
         $html = $filters[$i]->preFilter($html, $config, $context);
     }
     // purified HTML
     $html = $this->generator->generateFromTokens($this->strategy->execute($lexer->tokenizeHTML($html, $config, $context), $config, $context));
     for ($i = $filter_size - 1; $i >= 0; $i--) {
         $html = $filters[$i]->postFilter($html, $config, $context);
     }
     $html = HTMLPurifier_Encoder::convertFromUTF8($html, $config, $context);
     $this->context =& $context;
     return $html;
 }