Description:
------------
Attempting to use instances of class SplObjectStorage as an array results in 
exceptions and generally does not work as expected.

Test script:
---------------
$s = new SplObjectStorage;
$o = new stdClass;
$s[$o]["key"] = "value";
var_export($s[$o]);

// Fatal error: Uncaught exception 'UnexpectedValueException' with message 'Object not found'

Expected result:
----------------
The above sample code should create an array for the object key inside 
SplObjectStorage, and display:

array (
  'key' => 'value',
)

Compare the above code with: 

$s = array();
$o = "someKey";
$s[$o]["key"] = "value";
var_export($s[$o]);

which works as expected and displays

array (
  'key' => 'value',
)


Actual result:
--------------
Fatal error: Uncaught exception 'UnexpectedValueException' with message 'Object 
not found' in Command line code:1
Stack trace:
#0 Command line code(1): SplObjectStorage->offsetGet(Object(stdClass))
#1 {main}
  thrown in Command line code on line 1