So I thought I would just add +1 on to the data submitted from the PHP search page which works just great except for when you put 31 in as the day of the month, (so say we search from 01/01/2010 to 31/01/2010) it makes it into 32 and the querie returns 0 rows. However if I add an IF statement to not increment the day value by 1 if "31" is given as the last day in the query, we then only get results for 01/01/2010 to 30/01/2010.
is not INTERVAL the way to add a date, so it rolls over the month correctly
DATE_ADD('31/01/2010', 1 day) or '31/01/2010' + INTERVAL 1 day