In nearly every diary/calender it states the week numbers [#1 to #52] Are these used in the date function of PHP/MySQL? I need to pull out records stored in a database depending on what week they fell in.

It's for a shop' record of sales, so I need to pull out all sales done, for example, in: Nov 29 - Dec 5 or Dec 6 - Dec 12.

Is there an easy way to code this? The records are stored in the database width "date_of_sale" as a date field.