Basic PDO Questions

I have a three quick PDO questions. 1) If a PDOStatement is created within a function or method, is it's server result set connection is automatically freed up when the function returns (I assume so, but want to make sure)? 2) Does setting a PDOStatement to null (PDOStatement = null) terminate the server result set connection (I assume so, but want to make sure)? 3) The documentation for PDO::quote encourages us to use prepared statements over the PDO::query() or PDO::exec() methods citing the economy and portability of prepared statements. For queries that will run only once, is there significantly more overhead using prepared statements rather than the PDO::query() or PDO::exec() methods? I know that that's kind of an unclear/subjective question, but I just don't know how to state it better. Thanks, Chris D