$lat = 41.118491 // user's latitude
$lng = 25.404509 // user's longitude

SELECT *, 
( 6371 * acos( cos( radians($lat) ) 
* cos( radians( latitude ) ) 
* cos( radians( longitude ) - radians($lng) ) + sin( radians($lat) ) 
* sin( radians( latitude ) ) ) ) 
AS calculated_distance 
FROM settings as T 
HAVING calculated_distance <= (SELECT distance FROM settings WHERE sid=T.sid) 
ORDER BY distance_calc