Description:
------------
If there is an item in an array having key = 2^31-1 and you use [] operator without specifying a key it overflows and adds a new item with min. int (-2^31) in the array.

This is IMHO not correct or at least not consistent with the manual where the following sentence is stated:

"If you do not specify a key for a given value, then the maximum of the integer indices is taken, and the new key will be that maximum value + 1."

Moreover, consider the folowing array:
$a = array(2^31-2 => 1,-2^31 => 1) and use $a[] twice.
You get warning:
"Cannot add element to the array as the next element is already occupied".
But if the array is $a = array(2^31-1 => 1,-2^31 => 1) a new item is added with a key -2^31+1 with no warning.

However, if you use array_push instead [] it does never report a warning but does the same as [].

IMHO it will be more correct if both [] and array_push do not add a new key and report a warning or notice if the maximal integer key reaches maximum value 2^31-1.




Reproduce code:
---------------
    $a = array(2147483647 => 1, -2147483648 => 1);
    $a[] = 2;
    $a[] = 3;
    var_dump($a);
    
    $a = array(2147483646 => 1, -2147483648 => 1);
    $a[] = 2;
    $a[] = 3;
    var_dump($a);
  

Expected result:
----------------
Warning:  Cannot add element to array - integer key reached maximal possible value ...
Warning:  Cannot add element to array - integer key reached maximal possible value ...
array(4) {
  [2147483647]=>
  int(1)
  [-2147483648]=>
  int(1)
}

Warning:  Cannot add element to array - integer key reached maximal possible value ...
array(3) {
  [2147483646]=>
  int(1)
  [-2147483648]=>
  int(1)
  [2147483647]=>
  int(2)
}

Actual result:
--------------
array(4) {
  [2147483647]=>
  int(1)
  [-2147483648]=>
  int(1)
  [-2147483647]=>
  int(2)
  [-2147483646]=>
  int(3)
}
Warning:  Cannot add element to the array as the next element is already occupied in ...
array(3) {
  [2147483646]=>
  int(1)
  [-2147483648]=>
  int(1)
  [2147483647]=>
  int(2)
}