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 and , which can easily be styled with CSS. */ function diff($old, $new){ $maxlen=0; foreach($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( diff(array_slice($old, 0, $omax), array_slice($new, 0, $nmax)), array_slice($new, $nmax, $maxlen), diff(array_slice($old, $omax + $maxlen), array_slice($new, $nmax + $maxlen))); } function htmlDiff($old, $new){ $diff = diff(explode("\n", $old), explode("\n", $new)); $ret = ''; foreach($diff as $k){ if(is_array($k)) $ret .= (!empty($k['d'])?"~~".implode(' ',$k['d'])."~~ ":'').(!empty($k['i'])?"".implode(' ',$k['i'])." ":''); else $ret .= $k . ' '; } return $ret; } ?>

Old code

<?php echo $text1; ?>

New code

<?php echo $text2; ?>

Differences