Compare Two PHP Strings

I would like to implement a function that compares 2 strings and displays the different words with a different background (such as green if text is added or red if text is deleted).

This function would开发者_运维知识库 be similar to the difference between the original topic and the edited one on StackOverflow.

How would I do this?

I have a pure-PHP implementation here: Text version-control in PHP with difference highlight

You can use already written wdiff