I am trying to set up a class for tracking changes in the content by different authors. I did RnD and found text\_Diff is the pear package which is responsible for the same. Later, text\_diff is maintained at 

> 
> '<http://pear.horde.org/>'
> 
> 
> 

I am now trying to run the example

```
include_once "Text/Diff.php";
include_once "Text/Diff/Renderer.php";

$from_text=file('file.html');
$to_text=file('file_edited.html');

$diff = new Horde_Text_Diff($from_text, $to_text);
$renderer = new Horde_Text_Diff_Renderer();
echo $renderer->render($diff);

```

and I am getting the error 'Horde\_String'

I am not able to find class, any one has idea about this class?. There are multiple Engine like "Native","XDiff","String" and "Shell" ...but I am not able to find what are they and when you use which one..

any help to resolve this error will be a great help.

Thanks