protected function getValidReturnUri( $returnUri )
    {
        $match      = array();
        $returnUri  = ltrim( str_replace( '\\', '/', $returnUri ), "\n\r\t\v\e\f" );

        if ( ! preg_match( '#^/([^/].*)?$#', $returnUri, $match ) )
        {
            $returnUri = static::DEFAULT_RETURN_URI;
        }

        return $returnUri;
    }