//getDistance($lat1,$log1,$lat2,$log2)

function getDistance($a1,$b1,$a2,$b2)
{
$r = 3963.1; //3963.1 statute miles; 3443.9 nautical miles; 6378 km
$pi = 3.14159265358979323846;

//print "$a1, $b1, $a2, $b2, $r, $pi\n";
$a1 = $a1*($pi/180);
$a2 = $a2*($pi/180);
$b1 = $b1*($pi/180);
$b2 = $b2*($pi/180);

$ret = (acos(cos($a1)*cos($b1)*cos($a2)*cos($b2) + cos($a1)*sin($b1)*cos($a2)*sin($b2) + sin($a1)*sin($a2)) * $r) ;
//print "-- $ret--\n";
return $ret;
}