gistfile1.php

function nebula_audit_entity_update($entity, $type) {
  $orig_wrapper = entity_metadata_wrapper($type, $entity->original);
  $new_wrapper = entity_metadata_wrapper($type, $entity);
  $properties = $orig_wrapper->getPropertyInfo();
  $diffs = array();
  foreach ($properties as $key => $property) {
    $old = $orig_wrapper->$key->value();
    $new = $new_wrapper->$key->value();
    if ($old !== $new) {
      if (is_array($old)) {
        $diff = $property['label']." changed:<ul>";
        $added = array_diff($old, $new);
        foreach ($added as $item) {
          $diff .= "<li>".(string)$item." added</li>";
        }
        $subtracted = array_diff($new, $old);
        foreach($subtracted as $item) {
          $diff .= "<li>".(string)$item." removed</li>";
        }      
        $diff .="</ul>";
      } else {
        $diff = $property['label']." changed from '{$old}' to '${new}'";
      } 
    }
    if (!empty($diff)) {
      $diffs[] = $diff;
      unset($diff);
    }
  }
  $diffs = "<ul><li>" . implode("</li><li>", $diffs) . "</li><ul><br><br>";
  watchdog("nebula_audit", "Entity {$type}://{$entity} updated by {$GLOBALS['user']->mail}: {$diffs}", array(), WATCHDOG_INFO );
}