Formula to calculate distance of 2 corrdinats

$lat1 = 3.033555;
$lon1 = 101.87347;

$lat2 = $location['lat'];
$lon2 = $location['lon'];

$location['distance'] = (3958*3.1415926*sqrt(($lat2-$lat1)*($lat2-$lat1) + cos($lat2/57.29578)*cos($lat1/57.29578)*($lon2-$lon1)*($lon2-$lon1))/180);