Haversine Implementation in PHP with Coordinate Lookup from named addresses.

gistfile1.aw

<?php
function getCoordinatesFromAddress($address)
{
	if(!is_string($address)) return false;
	$result = false;
	
	if($result = file_get_contents('http://maps.google.com/maps?output=js&q=%s' . rawurlencode($address)))
	{
		if(strpos($result, 'errortips') > 1 || strpos($result, 'Did you mean:') !== false) return false;
		
		preg_match('!center:\s*{lat:\s*(-?\d+\.\d+),lng:\s*(-?\d+\.\d+)}!U', $result, $match);
		$coords['lat'] = $match[1];
		$coords['long'] = $match[2];
	}
	return $coords;
}

function haversine($lat1, $long1, $lat2, $long2, $radius)
{
	$distanceLat = deg2rad($lat2 - $lat1);
	$distanceLon = deg2rad($long2 - $long1);

	$a = sin($distanceLat / 2) * sin($distanceLat / 2) +
			sin($distanceLon / 2) * sin($distanceLon / 2) * cos(deg2rad($lat1)) * cos(deg2rad($lat2));

	$c = 2 * atan2(sqrt($a), sqrt(1 - $a));
	return $radius * $c;
}


define('EARTH_R_KM', 6371);
$wh = getCoordinatesFromAddress('1600 Pennsylvania Avenue, Washington D.C., DC 20500');
$ms = getCoordinatesFromAddress('Microsoft Corporation One Microsoft Way Redmond, WA 98052-6399');

echo haversine($wh['lat'], $wh['long'], $ms['lat'], $ms['long'], EARTH_R_KM) . ' Kilometers';

Haversine Formula

a = sin²(Δlat/2) + cos(lat1).cos(lat2).sin²(Δlong/2)
c = 2.atan2(√a, √(1−a))
d = R.c

Weird, Gist is messing up the whitespace.

Wow, so many problems with Gist right now. Had to re-edit this so many times.