Highlight the difference between two strings in PHP

What is the easiest way to highlight the difference between two strings in PHP?

I'm thinking along the lines of the Stack Overflow edit history page, where new text is in green and removed text is in red. If there are any pre-written functions or classes available, that would be ideal.

Solution 1:

Just wrote a class to compute smallest (not to be taken literally) number of edits to transform one string into another string:

http://www.raymondhill.net/finediff/

It has a static function to render a HTML version of the diff.

It's a first version, and likely to be improved, but it works just fine as of now, so I am throwing it out there in case someone needs to generate a compact diff efficiently, like I needed.

Edit: It's on Github now: https://github.com/gorhill/PHP-FineDiff

Solution 2:

You were able to use the PHP Horde_Text_Diff package.

However this package is no longer available.

Solution 3:

This is a nice one, also http://paulbutler.org/archives/a-simple-diff-algorithm-in-php/

Solving the problem is not as simple as it seems, and the problem bothered me for about a year before I figured it out. I managed to write my algorithm in PHP, in 18 lines of code. It is not the most efficient way to do a diff, but it is probably the easiest to understand.

It works by finding the longest sequence of words common to both strings, and recursively finding the longest sequences of the remainders of the string until the substrings have no words in common. At this point it adds the remaining new words as an insertion and the remaining old words as a deletion.

You can download the source here: PHP SimpleDiff...

Solution 4:

If you want a robust library, Text_Diff (a PEAR package) looks to be pretty good. It has some pretty cool features.