// php implementation from http://stackoverflow.com/questions/14750275/haversine-formula-with-php
I calculate distances straight inside queries, using the following stored procedure:

CREATE FUNCTION GEODIST (lat1 DOUBLE, lon1 DOUBLE, lat2 DOUBLE, lon2 DOUBLE)
    RETURNS DOUBLE
    DETERMINISTIC
        BEGIN
            DECLARE dist DOUBLE;
            SET dist =  round(acos(cos(radians(lat1))*cos(radians(lon1))*cos(radians(lat2))*cos(radians(lon2)) + cos(radians(lat1))*sin(radians(lon1))*cos(radians(lat2))*sin(radians(lon2)) + sin(radians(lat1))*sin(radians(lat2))) * 6378.8, 1);
            RETURN dist;
        END|
You just execute the above as an SQl statement from within phpMyAdmin to create the procedure. Just notice the ending |, so in your SQL input window, choose for the | sign as limiter.

Then in a query, call it like this:

$sql = "
SELECT `locations`.`name`, GEODIST(`locations`.`lat`, `locations`.`lon`, " . $lat_to_calculate . ", " . $lon_to_calculate . ") AS `distance`
FROM `locations` ";
I found this to be a lot faster than calculating it in PHP after the query has been run.