<?php
if (isset($_GET['lat']) && isset($_GET['lng'])) {
    $loc = true;
    $order = "distance";
    $campi = 'id_evento, ecc, ecc, ecc';
    $sql = "SELECT $campi,
       latitude, longitude, distance
      FROM (
         SELECT $campi,
            latitude,
            longitude,
            p.radius,
            p.distance_unit
                     * DEGREES(ACOS(COS(RADIANS(p.latpoint))
                     * COS(RADIANS((select latitude)))
                     * COS(RADIANS(p.longpoint - (select longitude)))
                     + SIN(RADIANS(p.latpoint))
                     * SIN(RADIANS((select latitude))))) AS distance
      FROM events JOIN (
            SELECT  ".mysql_real_escape_string($_GET['lat'])." AS latpoint,  -- latitudine dal quale calcolare le distanze
                    ".mysql_real_escape_string($_GET['lng'])." AS longpoint, -- longitudine dal quale calcolare le distanze
                    15.0 AS radius, -- il raggio in km
                    111.045 AS distance_unit
        ) AS p
      WHERE 1=1 -- qua le query normali, es id_evento=1
     ) AS d
     WHERE distance <= radius ";
}