is_reference?

ok, the idea is this foreach ( $_user_details as $key=>$value ) { $return_array["$key"] = &$_user_details["$key"]; } im doing that and i want that when $return_array gets updated and isnt a reference anymore to be able to add it to the sql for an update, thats no problem IF i can work out a way to test if its a reference or a new string to update the database with any suggestions? i know i can foreach and == test them but an is_reference would be faster if it existed :/ Cameron