Description:
------------
array_reduce() returns unexpected NULL (PHP 5.0-5.1.2 only)

Reproduce code:
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$array = array('value');
$result = array_reduce($array,'array_merge');
var_dump($result);

Expected result:
----------------
Works on PHP 4.4.0:
array(1) {
  [0]=>
  string(5) "value"
}

Actual result:
--------------
Tested on PHP 5.1.2:
NULL