Description:
------------
There are currently a number of places in the engine and library where the properties table is not properly separated. Essentially it's all the cases where get_properties() (or OBJPROP or HASH_OF) is used in a write context.

Two examples (assuming no immutable arrays):

$obj = (object) ['foo' => 1, 'bar' => 2];
foreach ($obj as $val) {
    var_dump($val);
    $obj->bar = 42;
}

This outputs 1, 1, 42 instead of 1, 42, because the properties table will be separated at the assignment, while it should have been separated at the start of the loop.

$arr = ['foo' => 1, 'bar' => 2];
$obj = (object) $arr;
next($obj);
var_dump(current($arr));

This outputs 2 instead of 1, because next() did not separate the properties HT, so it is still shared with the array.

I'm not sure how we should best fix this. We could always separate in get_properties(), however not all get_properties() uses are in write context. We can't cleanly separate outside get_properties(), as we'd have to assume how the properties are stored. The best option would likely be an extra argument to determine read/write context, but that's not ABI compatible.