Description:
------------
There's a memory leak when accessing an 
ArrayObject using array notation.

Reproduce code:
---------------
php -r '$a = new ArrayObject(array("a" => 1)); print $a["a"];'

This only seems to happen to string keys. There is no 
leak when I do:

php -r '$a = new ArrayObject(array("a")); print $a[0];'


Expected result:
----------------
1

Actual result:
--------------
1/usr/local/cvs/php-src/Zend/zend_execute.c(3382) :  
Freeing 0x00E14580 
(16 bytes), script=-
=== Total 1 memory leaks detected ===