added notes to reverse iterator in purge_relationships

api/fedora_item.inc

@@ -347,9 +347,10 @@ RDF;
     $modified = FALSE;
     $rels = $relsextxml->getElementsByTagNameNS($namespaceURI, $relationship);
     if (!empty($rels)) {
+      // iterate backwards so if we delete something our pointer doesn't get out of sync
       for ($i = $rels->length; $i>0; $i--) {
         $rel = $rels->item($i-1);
-//      foreach ($rels as $rel) {
+//      foreach ($rels as $rel) { // moving forward like this caused iteration errors when something was deleted
         if (  //If either no object is specified, or the object matches (in either the literal or URI case), remove this node from it's parent, and mark as changed.
           empty($object) || 
           (($literal_value == RELS_TYPE_URI) && $rel->getAttributeNS('http://www.w3.org/1999/02/22-rdf-syntax-ns#', 'resource') == $object) ||