Description:
------------
Specifying a simple callback for the filter_var_array function leads to invalid results.

Reproduce code:
---------------
function t($v){return $v;}
var_dump(filter_var_array(array("x"=>"s"), array("x"=>array("filter"=>FILTER_CALLBACK, "options"=>"t"))));

Expected result:
----------------
array(1) {
  ["x"]=>
  string(1) "s"
}

Actual result:
--------------
array(1) {
  ["x"]=>
  string(1) "("
}