<?php
function rad($x) { return $x * M_PI / 180.0;}
 
function distHaversine($lat1, $lon1, $lat2, $lon2) 
{
  $R = 6372.08; // earth's mean radius in km
  $dLat  = rad($lat2 - $lat1);
  $dLong = rad($lon2 - $lon1);
 
  $a = sin($dLat / 2.0) * sin($dLat / 2.0) +
          cos(rad($lat1)) * cos(rad($lat2)) * sin($dLong / 2.0) * sin($dLong / 2.0);
  $c = 2.0 * atan2(sqrt($a), sqrt(1.0 - $a));
  return $R * $c;
}
 
var_dump(distHaversine(1.57454123333,103.6200516333,1.57483825,103.619484475));

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