Check out the week() function from MySQL.
For example:
$sql = "SELECT * FROM table WHERE WEEK(date) = WEEK(NOW())";
Would return all the entries that are in this week, the 39th week of th year. All of them would range from 22-28.
To search for entries that are between that range, you can do something like this.
$sql = "SELECT * FROM table WHERE WEEK(date) BETWEEN WEEK($from) AND WEEK($to)";
Hope this helps.