     * @link http://github.com/paulgb/simplediff/blob/master/simplediff.php
     *
     * @access private
     * @param string $old The old block of data
     * @param string $new The new block of data
     */
    private function diff($old, $new) {
        $maxlen = 0;
        // Go through each old line.
        foreach ($old as $old_line => $old_value) {