Text_Diff_Engine_xdiff::diff

    function diff($from_lines, $to_lines)
    {
        array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
        array_walk($to_lines, array('Text_Diff', 'trimNewlines'));

        /* Convert the two input arrays into strings for xdiff processing. */
        $from_string = implode("\n", $from_lines);
        $to_string = implode("\n", $to_lines);

        /* Diff the two strings and convert the result to an array. */
        $diff = xdiff_string_diff($from_string, $to_string, count($to_lines));
        $diff = explode("\n", $diff);

        /* Walk through the diff one line at a time.  We build the $edits
         * array of diff operations by reading the first character of the
         * xdiff output (which is in the "unified diff" format).
         *
         * Note that we don't have enough information to detect "changed"
         * lines using this approach, so we can't add Text_Diff_Op_changed
         * instances to the $edits array.  The result is still perfectly
         * valid, albeit a little less descriptive and efficient. */
        $edits = array();
        foreach ($diff as $line) {
            if (!strlen($line)) {
                continue;
            }
            switch ($line[0]) {
            case ' ':
                $edits[] = new Text_Diff_Op_copy(array(substr($line, 1)));
                break;

            case '+':
                $edits[] = new Text_Diff_Op_add(array(substr($line, 1)));
                break;

            case '-':
                $edits[] = new Text_Diff_Op_delete(array(substr($line, 1)));
                break;
            }
        }

        return $edits;
    }