protected function getConfigurationFile()
    {
        if(!is_null($this->configPath)) {
            return realpath($this->configPath);
        } elseif(function_exists('base_path') and file_exists($phantomConfiguration = base_path() . DIRECTORY_SEPARATOR . 'SunPdf.js')) {
            return realpath($phantomConfiguration);
        } else {
            return realpath(__DIR__.'/../phantom.js');
        }
    }