Description:
------------
There is a test code:

  $a = array(0x7FFFFFFF => 42);
  $a[] = 37;
  var_dymp($a);

Second line emits warning:

  Warning: Cannot add element to the array as the next element
  is already occupied in ... on line 2

and doesn't add element with value 37. This is absolutely abnormal
behaviour. At least there is incorrect text for Warning. I expect,
the element should be added with any index (i.e. string "2147483648"
as the result of 0x7FFFFFFF+1 thru float), or something else. But
element was not added even.

Test script:
---------------
$a = array(0x7FFFFFFF => 42);
$a[] = 37;
var_dymp($a);

Expected result:
----------------
array(1) {
  [2147483647]=>
  int(42)
  ["2147483648"]=>
  int(37)
}

OR (when int will become int64):

array(1) {
  [2147483647]=>
  int(42)
  [2147483648]=>
  int(37)
}

Actual result:
--------------
Warning: Cannot add element to the array as the next element is already occupied in ... on line 2
array(1) {
  [2147483647]=>
  int(42)
}