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<?php
function sphere_distance($lat1, $lon1, $lat2, $lon2, $radius = 6378.135) {
$rad = doubleval(M_PI/180.0);
$lat1 = doubleval($lat1) * $rad;
$lon1 = doubleval($lon1) * $rad;
$lat2 = doubleval($lat2) * $rad;
$lon2 = doubleval($lon2) * $rad;
$theta = $lon2 - $lon1;
$dist = acos(sin($lat1) * sin($lat2) + cos($lat1) * cos($lat2) * cos($theta));
if ($dist < 0) { $dist += M_PI; }
return $dist = $dist * $radius;
}
$lat1 = 40.;
$lon1 = -50.;
$lat2 = 37;
$lon2 = -122;
$dist = sphere_distance($lat1, $lon1, $lat2, $lon2);
printf("%.2f\n", $dist * 0.621);
?>
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