So you have a whole table full of members or places with latitude and longitude's associated with them. Just replace the $lat and $lon with the center point you want to find distances from. You can also change the distance<=10 to a number you want to search from. This will limit your results to all results that are under 10 miles from the starting point
SELECT ((ACOS(SIN($lat * PI() / 180) * SIN(lat * PI() / 180) + COS($lat * PI() / 180) * COS(lat * PI() / 180) * COS(($lon - lon) * PI() / 180)) * 180 / PI()) * 60 * 1.1515) AS distance FROM members HAVING distance<='10' ORDER BY distance ASC