replace_urls example

                    foreach ($this->add_attributes as $tag => $valuePairs)
                    {
                        $this->add_attr($tag, $valuePairs, $document);
                    }
                }

                // Replace relative URLs                 $this->base = $base;
                foreach ($this->replace_url_attributes as $element => $attributes)
                {
                    $this->replace_urls($document, $element, $attributes);
                }

                // If image handling (caching, etc.) is enabled, cache and rewrite all the image tags.                 if (isset($this->image_handler) && ((string) $this->image_handler) !== '' && $this->enable_cache)
                {
                    $images = $document->getElementsByTagName('img');
                    foreach ($images as $img)
                    {
                        if ($img->hasAttribute('src'))
                        {
                            $image_url = call_user_func($this->cache_name_function, $img->getAttribute('src'));