array_search doesnt search the first index (0) of an array.
example:
url: test.php?action=new&state=ok&module=1

test.php:
...
$page_params=array_merge($HTTP_POST_VARS,$HTTP_GET_VARS);
//merge is not the problem

array_search("state",array_keys($page_params));
//result: true -> its ok

array_search("action",array_keys($page_params));
//result: false -> BUG

array_keys() works correct (I checked this), the problem is the array_search().