l3pp4rd/DoctrineExtensions — comment on commit 5c2c2302db76dcf16ce5e49fe15e8ec23ebc66c6
File:  line 0
By dbojdo:

It's ok when siblings are on level > 0. When siblings are on level 0 (have parent), switch above doesn't executed. So let's say: $item1 (lft 1, rgt 2, parent_id null), and $item2 (new one): persistAsNextSiblingOf($item2, $item1) causes that $item2 has parent ($item1).