Best way to get distance between users

Hi,

I need get distance between current user and a list of users, listing users by distance.

How can i do this?

Thanks,

I´m trying in advanced javascript, using this code:

function distance(lat1, lon1, lat2, lon2, unit) {

if ((lat1 == lat2) && (lon1 == lon2)) {

return 0;

}

else {

var radlat1 = Math.PI * lat1/180;

var radlat2 = Math.PI * lat2/180;

var theta = lon1-lon2;

var radtheta = Math.PI * theta/180;

var dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);

if (dist > 1) {

  dist = 1;

}

dist = Math.acos(dist);

dist = dist * 180/Math.PI;

dist = dist * 60 * 1.1515;

if (unit=="K") { dist = dist * 1.609344 }

if (unit=="N") { dist = dist * 0.8684 }

return dist;

}

}

This javascript is correct?

And logic is correct too?

Thanks