Adjust for PHP 8 negative array key change

Author: nikic

spec/10-expressions.md

@@ -888,9 +888,8 @@ and value of the result is the type and value of that element;
 otherwise, the result is `NULL`.
 
 If *expression* is omitted, a new element is inserted. Its key has type
-`int` and is one more than the highest, previously assigned, non-negative
-`int` key for this array. If this is the first element with a non-negative
-`int` key, key `0` is used.
+`int` and is one more than the highest, previously assigned `int` key for
+this array. If this is the first element with an `int` key, key `0` is used.
 If the largest previously assigned `int` key is the largest integer value that can be represented,
 the new element is not added.
 The result is the added new element, or `NULL` if the element was not added.

tests/expressions/postfix_operators/subscripting_2.phpt

@@ -11,7 +11,7 @@ var_dump($a);
 echo "------\n";
 
 $a = array(-30 => 33, -10 => -11);
-var_dump($a[] = 991);		// creates $a[0]
+var_dump($a[] = 991);		// creates $a[-9]
 var_dump($a);
 echo "------\n";
 
@@ -170,7 +170,7 @@ array(3) {
   int(33)
   [-10]=>
   int(-11)
-  [0]=>
+  [-9]=>
   int(991)
 }
 ------