Field Type Collation Attributes Null Default Extra Action
a int(2) Yes 0

they all have the same structure, thats copied and pasted straight from phpMyAdmin.

But like I said I dont understand why they work on one column and not the other.

Ill test the missing values theory, but I very much doubt that is the problem as if there was no value in $a/b there would be no error.

Solved!

See the missing values theory was wrong, but it lead me to go test the variables throughly and i solved it. Thanks!

In short said the variable had the wrong value (which it did not but anyways...) so I gave them all a default value of 0 at the start and override them with the real value and its working for the time being!