Description:
------------
Calling property_exists() on an ArrayObject gives a false result on when the value 
is a false value. This is not in compliance with the description of 
property_exists().

I tried this on PHP 5.3.2 and 5.3.3 under both Linux + Apache and Windows + IIS.

Test script:
---------------
$a = array('a' => 1, 'b'=> true, 'c' => 0, 'd' => null, 'e' => false, 
  'f' => array());
$o = new ArrayObject($a, ArrayObject::ARRAY_AS_PROPS);

foreach ($a as $key => $value) {
 echo $key . ': ' . (is_null($value) ? 'null' : $value) . 
    ' array_key_exists: ' . (array_key_exists($key, $a) ? 'true' : 'false') . 
    ' property_exists: ' . (property_exists($o, $key) ? 'true' : 'false');
}


Expected result:
----------------
a: 1 array_key_exists: true property_exists: true
b: 1 array_key_exists: true property_exists: true
c: 0 array_key_exists: true property_exists: true
d: null array_key_exists: true property_exists: true
e: array_key_exists: true property_exists: true
f: Array array_key_exists: true property_exists: true


Actual result:
--------------
a: 1 array_key_exists: true property_exists: true
b: 1 array_key_exists: true property_exists: true
c: 0 array_key_exists: true property_exists: false
d: null array_key_exists: true property_exists: false
e: array_key_exists: true property_exists: false
f: Array array_key_exists: true property_exists: false