src/Diff.php
protected function lineMode($text1, $text2, $deadline)
    {
        // Scan the text on a line-by-line basis first.
        list($text1, $text2, $lineArray) = $this->getToolkit()->linesToChars($text1, $text2);

        $diff = new Diff();
        $diff->main($text1, $text2, false, $deadline);
        $diffs = $diff->getChanges();

        // Convert the diff back to original text.
        $this->getToolkit()->charsToLines($diffs, $lineArray);
        $diff->setChanges($diffs);

        // Eliminate freak matches (e.g. blank lines)
        $diff->cleanupSemantic();
        $diffs = $diff->getChanges();

        // Rediff any replacement blocks, this time character-by-character.
        // Add a dummy entry at the end.
        array_push($diffs, array(self::EQUAL, ''));
        $pointer = 0;
        $countDelete = 0;
        $countInsert = 0;
        $textDelete = '';
        $textInsert = '';

        while ($pointer < count($diffs)) {
            switch ($diffs[$pointer][0]) {
                case self::DELETE:
                    $countDelete++;
                    $textDelete .= $diffs[$pointer][1];
                    break;
                case self::INSERT:
                $countInsert++;
                    $textInsert .= $diffs[$pointer][1];
                    break;
                case self::EQUAL:
                    // Upon reaching an equality, check for prior redundancies.
                    if ($countDelete > 0 && $countInsert > 0) {
                        // Delete the offending records and add the merged ones.
                        $subDiff = new Diff();
                        $subDiff->main($textDelete, $textInsert, false, $deadline);
                        array_splice($diffs, $pointer - $countDelete - $countInsert, $countDelete + $countInsert, $subDiff->getChanges());
                        $pointer = $pointer - $countDelete - $countInsert + count($subDiff->getChanges());
                    }
                    $countDelete = 0;
                    $countInsert = 0;
                    $textDelete = '';
                    $textInsert = '';
                    break;
            }
            $pointer++;
        }

        // Remove the dummy entry at the end.
        array_pop($diffs);

        return $diffs;
    }
protected function lineMode($text1, $text2, $deadline)
    {
        // Scan the text on a line-by-line basis first.
        list($text1, $text2, $lineArray) = $this->getToolkit()->linesToChars($text1, $text2);

        $diff = new Diff();
        $diff->main($text1, $text2, false, $deadline);
        $diffs = $diff->getChanges();

        // Convert the diff back to original text.
        $this->getToolkit()->charsToLines($diffs, $lineArray);
        $diff->setChanges($diffs);

        // Eliminate freak matches (e.g. blank lines)
        $diff->cleanupSemantic();
        $diffs = $diff->getChanges();

        // Rediff any replacement blocks, this time character-by-character.
        // Add a dummy entry at the end.
        array_push($diffs, array(self::EQUAL, ''));
        $pointer = 0;
        $countDelete = 0;
        $countInsert = 0;
        $textDelete = '';
        $textInsert = '';

        while ($pointer < count($diffs)) {
            switch ($diffs[$pointer][0]) {
                case self::DELETE:
                    $countDelete++;
                    $textDelete .= $diffs[$pointer][1];
                    break;
                case self::INSERT:
                $countInsert++;
                    $textInsert .= $diffs[$pointer][1];
                    break;
                case self::EQUAL:
                    // Upon reaching an equality, check for prior redundancies.
                    if ($countDelete > 0 && $countInsert > 0) {
                        // Delete the offending records and add the merged ones.
                        $subDiff = new Diff();
                        $subDiff->main($textDelete, $textInsert, false, $deadline);
                        array_splice($diffs, $pointer - $countDelete - $countInsert, $countDelete + $countInsert, $subDiff->getChanges());
                        $pointer = $pointer - $countDelete - $countInsert + count($subDiff->getChanges());
                    }
                    $countDelete = 0;
                    $countInsert = 0;
                    $textDelete = '';
                    $textInsert = '';
                    break;
            }
            $pointer++;
        }

        // Remove the dummy entry at the end.
        array_pop($diffs);

        return $diffs;
    }
Do a quick line-level diff on both strings, then rediff the parts for greater accuracy.
This speedup can produce non-minimal diffs.

@param string $text1    Old string to be diffed.
@param string $text2    New string to be diffed.
@param int    $deadline Time when the diff should be complete by.

@return array Array of changes.