Description:
------------
If the current element of a RecursiveIteratorIterator has no children then callGetChildren() causes an error message like

Fatal error: Uncaught exception 'InvalidArgumentException' with message 'Passed variable is not an array or object, using empty array instead' 

This is confusing because the PHP code does not pass an argument here.

I think that either the method should return null when there are no children - or at least the error message could be clearer.

This has been found as part of phptestfest 09 - an XFail test will be commited from PHPLondon

My Apologies if this is expected behaviour, I realise the code is undocumented, but I wanted to commit a test to cover this and filing a bug seemed the best way to confirm one way or the other :-)

Reproduce code:
---------------
<?php
  $array = array(array(7,8,9),1,2,3,array(4,5,6));
$recursiveArrayIterator = new RecursiveArrayIterator($array);
$test = new RecursiveIteratorIterator($recursiveArrayIterator);

var_dump($test->current());
$test->next();
var_dump($test->current());
try {
  $output = $test->callGetChildren();
} catch (InvalidArgumentException $ilae){
  $output = null;  
  print "invalid argument exception\n";
}
var_dump($output);
?>

Expected result:
----------------
array(3) {
  [0]=>
  int(7)
  [1]=>
  int(8)
  [2]=>
  int(9)
}
int(7)
NULL

Actual result:
--------------
array(3) {
  [0]=>
  int(7)
  [1]=>
  int(8)
  [2]=>
  int(9)
}
int(7)
invalid argument exception
NULL