Hi All. Never registered, but been browsing around in here for a while now.

I've been charged with getting a visual html diff. The closest I've found is a python script. Unfortunately our host will not install mod_python and we have limited control over .ht* files. Could someone familiar with both python and php possibly convert this script? I've been working on this myself but am totally confused and lost...

import difflib, string

def isTag(x): return x[0] == "<" and x[-1] == ">"

def textDiff(a, b):
    """Takes in strings a and b and returns a human-readable HTML diff."""

    out = []
    a, b = html2list(a), html2list(b)
    s = difflib.SequenceMatcher(None, a, b)
    for e in s.get_opcodes():
        if e[0] == "replace":
            # @@ need to do something more complicated here
            # call textDiff but not for html, but for some html... ugh
            # gonna cop-out for now
            out.append('<del class="diff modified">'+''.join(a[e[1]:e[2]]) + '</del><ins class="diff modified">'+''.join(b[e[3]:e[4]])+"</ins>")
        elif e[0] == "delete":
            out.append('<del class="diff">'+ ''.join(a[e[1]:e[2]]) + "</del>")
        elif e[0] == "insert":
            out.append('<ins class="diff">'+''.join(b[e[3]:e[4]]) + "</ins>")
        elif e[0] == "equal":
            out.append(''.join(b[e[3]:e[4]]))
        else: 
            raise "Um, something's broken. I didn't expect a '" + `e[0]` + "'."
    return ''.join(out)

def html2list(x, b=0):
    mode = 'char'
    cur = ''
    out = []
    for c in x:
        if mode == 'tag':
            if c == '>': 
                if b: cur += ']'
                else: cur += c
                out.append(cur); cur = ''; mode = 'char'
            else: cur += c
        elif mode == 'char':
            if c == '<': 
                out.append(cur)
                if b: cur = '['
                else: cur = c
                mode = 'tag'
            elif c in string.whitespace: out.append(cur+c); cur = ''
            else: cur += c
    out.append(cur)
    return filter(lambda x: x is not '', out)

if __name__ == '__main__':
    import sys
    try:
        a, b = sys.argv[1:3]
    except ValueError:
        print "htmldiff: highlight the differences between two html files"
        print "usage: " + sys.argv[0] + " a b"
        sys.exit(1)
    print textDiff(open(a).read(), open(b).read())

Hokay... The real crux of this script is a library called difflib. In fact, all the hard comparison work between the two strings is done in just one line:

PHP Code:

difflib.SequenceMatcher(None, a, b) 


All the rest of that is just telling the script how to properly conduct itself and how to handle the results of what difflib does.
Building an equivalent in php would therefore be very simple - if you can find an equivalent library for php. Otherwise there'd be some pretty hardcore scripting ahead.
Hope this helps, Tom
PS If you do find a library in php, I'll happily build up the rest of the script around it.