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. */ /** * Diff checker * * @since 4.0.1 */ function wpappninja_diff($old, $new){ $old = preg_replace('#<#', '<', $old); $new = preg_replace('#<#', '<', $new); $old = preg_replace('#>#', '>', $old); $new = preg_replace('#>#', '>', $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( wpappninja_diff(array_slice($old, 0, $omax), array_slice($new, 0, $nmax)), array_slice($new, $nmax, $maxlen), wpappninja_diff(array_slice($old, $omax + $maxlen), array_slice($new, $nmax + $maxlen))); } function wpappninja_html_diff($old, $new, $title = ""){ if ($old == $new) {return;} $ret = '


' . $title . '

'; $ret .= '

OLD

' . $old . '

NEW

' . $new . '

DIFF

'; $diff = wpappninja_diff(preg_split("/[\s]+/", $old), preg_split("/[\s]+/", $new)); foreach($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; }