HTMLPurifier_URI::toString PHP Method

    public function toString()
    {
        // reconstruct authority
        $authority = null;
        // there is a rendering difference between a null authority
        // (http:foo-bar) and an empty string authority
        // (http:///foo-bar).
        if (!is_null($this->host)) {
            $authority = '';
            if (!is_null($this->userinfo)) {
                $authority .= $this->userinfo . '@';
            }
            $authority .= $this->host;
            if (!is_null($this->port)) {
                $authority .= ':' . $this->port;
            }
        }
        // Reconstruct the result
        // One might wonder about parsing quirks from browsers after
        // this reconstruction.  Unfortunately, parsing behavior depends
        // on what *scheme* was employed (file:///foo is handled *very*
        // differently than http:///foo), so unfortunately we have to
        // defer to the schemes to do the right thing.
        $result = '';
        if (!is_null($this->scheme)) {
            $result .= $this->scheme . ':';
        }
        if (!is_null($authority)) {
            $result .= '//' . $authority;
        }
        $result .= $this->path;
        if (!is_null($this->query)) {
            $result .= '?' . $this->query;
        }
        if (!is_null($this->fragment)) {
            $result .= '#' . $this->fragment;
        }
        return $result;
    }

 /**
  * @param HTMLPurifier_URI $uri
  * @param HTMLPurifier_Config $config
  * @param HTMLPurifier_Context $context
  * @return bool
  */
 public function filter(&$uri, $config, $context)
 {
     // check if filter not applicable
     if (!$config->get('HTML.SafeIframe')) {
         return true;
     }
     // check if the filter should actually trigger
     if (!$context->get('EmbeddedURI', true)) {
         return true;
     }
     $token = $context->get('CurrentToken', true);
     if (!($token && $token->name == 'iframe')) {
         return true;
     }
     // check if we actually have some whitelists enabled
     if ($this->regexp === null) {
         return false;
     }
     // actually check the whitelists
     if (!preg_match($this->regexp, $uri->toString())) {
         return false;
     }
     // Make sure that if we're an HTTPS site, the iframe is also HTTPS
     if (is_https() && $uri->scheme == 'http') {
         // Convert it to a protocol-relative URL
         $uri->scheme = null;
     }
     return $uri;
 }