<?
$myarray['105'] = 'Hello';
$myarray[(string)'106'] = 'Goodbye';
var_dump($myarray);
?>

array(2) {
  [105]=>
  string(5) "Hello"
  [106]=>
  string(7) "Goodbye"
}

It shouldn't be auto-converting array keys to numbers if they're already of a different type! Let's say I have an whole list of items as my array keys, and one just happens to be "able" to be converted into a number. Suddenly one of my array keys is no longer a string.