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

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.