Description:
------------
Numeric keys in object convert as string keys to array.
And I can't access to this keys after conversion, because PHP automatic convert string numeric keys to integer.
In 7.1 too...

Test script:
---------------
$a=new stdClass();

$a->{1}=1;
$a->{2}=2;
$a->{3}=3;

$b=(array)$a;

var_dump([$b,1,@$b[1]]);

-----------------------------------------
  [0]=>
  array(3) {
    ["1"]=>
    int(1)
    ["2"]=>
    int(2)
    ["3"]=>
    int(3)
  }
  [1]=>
  int(1)
  [2]=>
  NULL