This is the ToDo of ext/spl:

- spl::array_access cals set() which is supposed to return a value.
  Currently you *must* return a value even when it is not used.
    $obj[$idx] = $val;      // doesn't use the return value
    $x = $obj[$idx] = $val; // here it is used
  Since array_access.phpt is a test with a return value there
  should be a test without a return value. Maybe an error message
  is required in case there is no return value.

- spl::array_access_ex is not completely done and not tested.

If you have further questions: mailto:helly@php.net