v318 db parser bug (maybe, perhaps)

up to and including v312, i was able to use queries like the following

PHP Code:

SELECT ..... FROM .... WHERE (a.transdate >= "?") AND (p.prva_id>0) AND (p.prod_id=?) 


Today i made the quantum leap to v318 and such queries crash on the part "(p.prod_id=?)".
Now it will only work if i use (p.prod_id="?") ie enclose the question mark in quotes
Switch back to v312 and it's ok
I don't know if this is a bug or if I've just been lucky in always getting away with sloppy coding.
The quotes are needed for e.g. a date or text but I've never had to use them for integers
Bill