Detect difference between two texts

Hi, I have two text variables: $html_1 $html_2 They both contain a lot of HTML code. I want a PHP script that will work its way through each of these highlighting and identifying the differences. You can see an example of what Im look for at: <[login to view URL]> I want something that is formatted like that. (showing both files side by side, highlying areas that have been changed along with the actual changes) Accuracy is also important. You may find the following resources useful: <[login to view URL]> <[login to view URL]> Any questions, please ask. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform PHP, Apache.