if (arg(0) == 'node' && is_numeric(arg(1))) {
  $node = node_load(arg(1));
  return $node->field_proj_parent_ref[0][nid];
} else {
  return FALSE;
}

Use this to pull a list of items based on the nid of the 'parent' node.... so you can show fields added to that node, on the child. Handy.

Make nid argument..... use custom php arg code below to feed the argument the nid of the parent.

Remember to change the $ to the field name you are targeting..... IMPORTANT

Views node relationship argument

drupal

PHP