When one my PHP scripts insert something into the database and something in a column that is an int is null I get this error: Incorrect integer value: '' for column 'collar_invid' at row 1

God, this didn't happen on my last server! Before I had my own server I was using MySQL 4. something (it's the one that comes with Plesk). and I didn't have this problem. But now I have my own server with MySQL 5.1 installed on it and it does this...how do I "turn this off"?