Revision comparision in PHP

Question

Say, I have var1 and var2 both with a string value. Var2 is a revision of var1 with minor changes: var1:

Hello, world1

var2:

Bye bye, world!

Now I want this output:

<span class="removed">Hello</span> <span class="new">Bye bye</span>, world<span class="removed">1</span><span class="new">!</span>

much like SO's way. How can I do this in php?

Thanks

Answer 1

I would suggest you take a look at Text_Diff on PEAR.

Answer 2

Longest common subsequence problem. Once I found nice implementation in Python and translated it into PHP (because PHP arrays are quite memory expensive I had to sacrifice speed by using string to hold LCS matrix).