haversine great circle query

<?php
//  111.045 -- kms
//  69.0 -- miles

$sql=
"
   SELECT
    id, nama, lat, lng, distance
   FROM (
     SELECT a.id,
            a.nama,
            a.poskode,
            a.lat,
            a.lng,
            b.radius,
            111.045
             * DEGREES(ACOS(COS(RADIANS(b.latpoint))
             * COS(RADIANS(a.lat))
             * COS(RADIANS(b.longpoint - a.lng))
             + SIN(RADIANS(b.latpoint))
             * SIN(RADIANS(a.lat)))) AS distance
      FROM
        wilayah AS a
        JOIN
        (
          SELECT
            {$org_lat} AS latpoint,
            {$org_lng} AS longpoint,
            {$ini_rad} AS radius,
        ) AS b ON 1=1
      WHERE
        a.lat BETWEEN
            b.latpoint  - (b.radius / b.distance_unit)
            AND b.latpoint  + (b.radius / b.distance_unit)
        AND a.lng BETWEEN
          b.longpoint - (b.radius / (b.distance_unit * COS(RADIANS(b.latpoint))))
          AND b.longpoint + (b.radius / (b.distance_unit * COS(RADIANS(b.latpoint))))
     ) AS d
   WHERE distance <= radius
   ORDER BY distance
   LIMIT 15
";