This post is from one of our customers!
Looking forward to that free shirt! In the mean time, here's a fun sql snippet I wrote to find select users (for something I was working on) by radius of area:
SELECT
location.id,location.name,location.address,count(distinct user.id) as user,
(
6371 * acos(
cos( radians( your.latitude )) *
cos( radians( location.lat )) *
cos( radians( location.lat ) - radians( your.longtitude )) +
sin( radians( your.latitude )) *
sin( radians( location.long ))
)
) `distance`
FROM
location LEFT JOIN user ON location.id=user.location_id
GROUP BY
location.id
HAVING
`distance` < 100
ORDER BY
`distance`
LIMIT
25
