<?php
/*
Paul's Simple Diff Algorithm v 0.1
(C) Paul Butler 2007 <http://www.paulbutler.org/>
May be used and distributed under the zlib/libpng license.
This code is intended for learning purposes; it was written with short
code taking priority over performance. It could be used in a practical
application, but there are a few ways it could be optimized.
Given two arrays, the function diff will return an array of the changes.
I won't describe the format of the array, but it will be obvious
if you use print_r() on the result of a diff on some test data.
htmlDiff is a wrapper for the diff command, it takes two strings and
returns the differences in HTML. The tags used are <ins> and <del>,
which can easily be styled with CSS.
*/
class pdiff {
//
static function diff($old, $new){
$matrix = array();
$maxlen = 0;
foreach($old as $oindex => $ovalue){
$nkeys = array_keys($new, $ovalue);
foreach($nkeys as $nindex){
$matrix[$oindex][$nindex] = isset($matrix[$oindex - 1][$nindex - 1]) ?
$matrix[$oindex - 1][$nindex - 1] + 1 : 1;
if($matrix[$oindex][$nindex] > $maxlen){
$maxlen = $matrix[$oindex][$nindex];
$omax = $oindex + 1 - $maxlen;
$nmax = $nindex + 1 - $maxlen;
}
}
}
if($maxlen == 0) return array(array('d'=>$old, 'i'=>$new));
return array_merge(
pdiff::diff(array_slice($old, 0, $omax), array_slice($new, 0, $nmax)),
array_slice($new, $nmax, $maxlen),
pdiff::diff(array_slice($old, $omax + $maxlen), array_slice($new, $nmax + $maxlen)));
}
// markup <ins> and <del> between old and new text blob
static function htmlDiff($old, $new){
$ret = '';
$diff = pdiff::diff(preg_split("/[\s]+/", $old), preg_split("/[\s]+/", $new));
foreach($diff as $k){
if(is_array($k)) {
$ret .=
(!empty($k['d']) ? "<del>" . input::html(implode(' ',$k['d'])) . "</del> " : '').
(!empty($k['i']) ? "<ins>" . input::html(implode(' ',$k['i'])) . "</ins> " : '');
}
else {
$ret .= input::html($k) . ' ';
}
}
return $ret;
}
// Just compare word-wise without between three revisions, without honoring order
static function triDiff($prev, $curr, $next){
$ret = '';
$prev = preg_split("/[\s]+/", $prev);
$curr = preg_split("/[\s]+/", $curr);
$next = preg_split("/[\s]+/", $next);
foreach($curr as $word){
if (!in_array($word, $prev)) {
$ret .= "<ins>$word</ins> ";
}
elseif (!in_array($word, $next)) {
$ret .= "<del>$word</del> ";
}
else {
$ret .= "$word ";
}
}
return $ret;
}
}
?>