in case anyone was wondering
something like
$val = 5;
$sql = "REPLACE table (column) VALUES (:val)";
$stmt = $dbh->prepare($sql);
$stmt->bindParam(':val', $val, PDO::PARAM_INT);
$stmt->execute();
$lastId = $dbh->lastInsertId();
will return the last inserted id, whether the record was replaced or simply inserted
the REPLACE syntax, simply inserts, or deletes > inserts
so lastInsertId() still works
refer to http://mysql.com/doc/refman/5.0/en/replace.html
for REPLACE usage