public function execute()
    {
        try
        {
            if (!$this->_prepared) {
                // includes generated template PHP code
                $this->prepare();
            }
            $this->_context->echoDeclarations(false);

            $templateFunction = $this->getFunctionName();

            try {
                ob_start();
                $templateFunction($this, $this->_context);
                $res = ob_get_clean();
            }
            catch (Exception $e)
            {
                ob_end_clean();
                throw $e;
            }

            // unshift doctype
            if ($this->_context->_docType) {
                $res = $this->_context->_docType . $res;
            }

            // unshift xml declaration
            if ($this->_context->_xmlDeclaration) {
                $res = $this->_context->_xmlDeclaration . "\n" . $res;
            }

            if ($this->_postfilter) {
                return $this->_postfilter->filter($res);
            }
        }
        catch (Exception $e)
        {
            PHPTAL_ExceptionHandler::handleException($e, $this->getEncoding());
        }

        return $res;
    }