DB, prepare() and NULL values

All morning I've been trying to somehow work it so that prepare() recognizes and accounts for NULL values. Such that if I set a variable as NULL and NULL being a valid value for a field in the table, it would prepare the query so that it generates it using NULL. For example, say I had the following: $sth = $db->prepare('INSERT INTO numbers (number) VALUES (?)'); $res =& $db->execute($sth, 1); PEAR DB would generate a query looking like: INSERT INTO numbers (number) VALUES ('1') Now, let's say that the number column was set to allow null values. Here is the same code, slighly altered: $sth = $db->prepare('INSERT INTO numbers (number) VALUES (?)'); $res =& $db->execute($sth, NULL); Now the generated query would look like: INSERT INTO numbers (number) VALUES ('') when I need it to look like: INSERT INTO numbers (number) VALUES (NULL) I've tried changing the placeholder from a ? to a ! but all that did was make it so that there was no value set making the query look like: INSERT INTO numbers (number) VALUES () would would cause an error, particularly if there was more than just 1 column set up in the query. And changing the placeholder to a & only resulted in getting back an error object saying something about insufficient permissions. So I'm curious, is what I am trying to do even possible? I've looked at the source code in DB_common and it appears that I'm SOL. Has anyone else had any success in doing what I'm trying to do? thnx, Chris