private function getFreeKey()
    {
        $index = count($this->maps);

        while (isset($this->maps[$index]))
            $index++;

        return $index;
    }
private function getFreeKey()
    {
        $index = count($this->maps);

        while (isset($this->maps[$index]))
            $index++;

        return $index;
    }
private function getFreeKey ( ) { $ index = count ( $ this -> maps ) ; while ( isset ( $ this -> maps [ $ index ] ) ) $ index ++ ; return $ index ; }
Generate a defineMap key not already taken
@return int
Generate a defineMap key not already taken