Description:
------------
The behavior of operator [] to the array is sometimes strange or hard to describe the specification. For instance, the array which has two index, 2147483647 and -2147483648 on 32bit environment gets strange results. See below example:

Reproduce code:
---------------
<?php
$array=array();
$array[-2147483648]=2;
$array[2147483647]=1;
$array[]=3;
var_dump($array);

$array=array();
$array[2147483647]=1;
$array[-2147483648]=2;
$array[]=3;
var_dump($array);

Expected result:
----------------
It should be same behavior. I think, the substitution to $array[] shuold be both failed for this case.

Actual result:
--------------
PHP Warning:  Cannot add element to the array as the next element is already occupied in ./array-maxint-test.php on line 5
array(2) {
  [-2147483648]=>
  int(2)
  [2147483647]=>
  int(1)
}
array(3) {
  [2147483647]=>
  int(1)
  [-2147483648]=>
  int(2)
  [-2147483647]=>
  int(3)
}