Calculate distance between two zipcodes

//Get distance between two zipcodes
function distance($lat1, $lon1, $lat2, $lon2, $unit) {
	if (($lat1 == $lat2) && ($lon1 == $lon2)) {
		return 0;
	} else {
		$theta = $lon1 - $lon2;
		$dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) +  cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
		$dist = acos($dist);
		$dist = rad2deg($dist);
		$miles = $dist * 60 * 1.1515;
		$unit = strtoupper($unit);

      //mesuremenrt in km,nautical miles
	  if ($unit == "K") {
	      return ($miles * 1.609344);//in km
	  } else if ($unit == "N") {
	      return ($miles * 0.8684);//in nm
	  } else {
	      return $miles; //in miles
	  }
	}
}

//Example of usage:
distance($lat1, $lon1, $lat2, $lon2, "M");

Get lat long

//For Zipcode two
$url2 = "https://maps.googleapis.com/maps/api/geocode/json?key=". $google ."&address=" . $zipcode . "&sensor=false";

$ch2 = curl_init();
curl_setopt($ch2,CURLOPT_URL, $url2);
curl_setopt($ch2,CURLOPT_POST, true);
curl_setopt($ch2,CURLOPT_POSTFIELDS, '');
curl_setopt($ch2, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch2, CURLOPT_HEADER, false);
$result2 = curl_exec($ch2);
curl_close($ch2);

$decode2 = json_decode($result2, true);
$res12[] = $decode2['results'][0];
$res22[] = $res12[0]['geometry'];
$res32[] = $res22[0]['location'];