PHP Sorting nearest coordinates

Question

I have a MySQL table in a PHP webservice containing longitude and latitude. I want to send the user only the, let\'s say, 5 closest coordinates. I wrote the method which cal

Answer 1

Using Google's algorithm:

$lon = //your longitude
$lat = //your latitude
$miles = //your search radius

$query = "SELECT *, 
( 3959 * acos( cos( radians('$lat') ) * 
cos( radians( latitude ) ) * 
cos( radians( longitude ) - 
radians('$lon') ) + 
sin( radians('$lat') ) * 
sin( radians( latitude ) ) ) ) 
AS distance FROM yourtable HAVING distance < '$miles' ORDER BY distance ASC LIMIT 0, 5"

latitude and longitude in this query are going to be your lat/lon column names.

Answer 2

I've encountered same problem lately. What i've decided was to write a mysql function to calculate distance and then use it in sql query. Mysql function:

CREATE FUNCTION distance(lat1 float, lon1 float, lat2 float, lon2 float) 
RETURNS float
RETURN ACOS(SIN(RADIANS(lat1))*SIN(RADIANS(lat2))+COS(RADIANS(lat1))*COS(RADIANS(lat2))*COS(RADIANS(lon2-lon1)))*6371

If your Coordinates table has columns f.e. latitude and longitude then the code might look like this:

$q = mysql_query("SELECT * FROM Coordinates ORDER BY 
     distance(latitude, longitude, $lat, $lon) LIMIT 5";

Where $lat and $lon contain provided location.

Answer 3

It is more efficient to embed the sort in the query.

This wonderful tutorial will help you (and provides a query that serves your needs): https://developers.google.com/maps/articles/phpsqlsearch_v3#findnearsql