I am not fully understaing what is not working, but here are some things I have noticed that may be messing with things:
-Is your query returning with anything? Because your sprintf is looking for the string while you appear to be needing an integer.
-You check cat_result before your assign it, you also dont use a $ sign.

Your program will most likely die nothing (mysql_error will be blank) every time since you are checking a blank variable for being blank. It could also be of error that sprintf may be canceling the value out (this is, among other reasons, why I don't use sprintf).

__________________