MySQL server parameters default empty string to null How can I set MySQL server parameters to default empty strings to null on insert?

is this possible?
There is no way to do that by changing a server parameter. NULL is different from an empty string so there is no reason to have that.

You could change your application to send NULL to your SQL statement or add a condition to your query.

INSERT INTO table (column1) values (IF(LENGTH('$variable')=0,NULL,'$variable'));