function highlight_lines_extra($lines, $style = null)
    {
        if (is_array($lines)) {
            //Split up the job using single lines at a time
            foreach ($lines as $line) {
                $this->highlight_lines_extra($line, $style);
            }
        }
        else {
            //Mark the line as being highlighted specially
            $lines = intval($lines);
            $this->highlight_extra_lines[$lines] = $lines;

            //Decide on which style to use
            if ($style === null) { //Check if we should use default style
                unset($this->highlight_extra_lines_styles[$lines]);
            }
            elseif ($style === false) { //Check if to remove this line
                unset($this->highlight_extra_lines[$lines]);
                unset($this->highlight_extra_lines_styles[$lines]);
            }
            else {
                $this->highlight_extra_lines_styles[$lines] = $style;
            }
        }
    }