Tag: distancematrix

The postcode code has been updated to use Google’s distancematrix api, which provides a very different set of data from the old “as the bird flies” calculation (it calculates road distance, and provides transport options etc).

The following code is merely a demonstration, which can be seen here.

<?php
// Specify Postcodes to Geocode
$postcode1 = 'BH151DA';
$postcode2 = 'BH213AP';

// Set and retrieve the query URL
$request = "http://maps.googleapis.com/maps/api/distancematrix/json?origins=" . $postcode1 . "&destinations=" . $postcode2 . "&mode=driving&language=en-GB&sensor=false&units=imperial";
$distdata = file_get_contents($request);

// Put the data into an array for easy access
$distances = json_decode($distdata, true);

// Do some error checking, first for if the response is ok
$status = $distances["status"];
$row_status = $distances["rows"][0]["elements"][0]["status"];

if ($status == "OK" && $row_status == "OK") {

// Calculate the distance in miles
$distance = $distances["rows"][0]["elements"][0]["distance"]["value"];
$distance_miles = round($distance * 0.621371192/1000, 2);

echo 'The distance between '.$postcode1.' and '.$postcode2.' is '.($distance/1000).'Km ('.$distance_miles.' miles).';

} else {
    echo "Calculating the distance between your locations caused an error.";
}

?>

Having better error checking would also be a good idea if you plan to use the above code. Using &unit=imperial is optional, as Google always returns metres – so the code runs a basic calculation on these to convert to miles.

UPDATE: A new version which calculates distance based on roads is available.

If you’re looking to make any kind of radius checker, delivery calculator etc, you will need to have some method of calculating this distance. Unfortunately for us in the UK, Royal Mail keep a tight grip on postcode data.

As a result, the best low-budget way of finding postcodes is by using the Google Maps api – which in itself isn’t 100% accurate (but good enough).

So we can use the following code:

<?php
// Specify Postcodes to Geocode
$postcode1 = 'BH151DA';
$postcode2 = 'BH213AP';

// Geocode Postcodes & Get Co-ordinates 1st Postcode
$pc1 = 'http://maps.google.com/maps/geo?q='.$postcode1.',+UK&output=csv&sensor=false';
$data1 = @file_get_contents($pc1);
$result1 = explode(",", $data1);
$custlat1 = $result1[2];
$custlong1 = $result1[3];

// Geocode Postcodes & Get Co-ordinates 2nd Postcode
$pc2 = 'http://maps.google.com/maps/geo?q='.$postcode2.',+UK&output=csv&sensor=false';
$data2 = @file_get_contents($pc2);
$result2 = explode(",", $data2);
$custlat2 = $result2[2];
$custlong2 = $result2[3];

// Work out the distance!
$pi80 = M_PI / 180;
$custlat1 *= $pi80;
$custlong1 *= $pi80;
$custlat2 *= $pi80;
$custlong2 *= $pi80;

$r = 6372.797; // mean radius of Earth in km
$dlat = $custlat2 - $custlat1;
$dlng = $custlong2 - $custlong1;
$a = sin($dlat / 2) * sin($dlat / 2) + cos($custlat1) * cos($custlat2) * sin($dlng / 2) * sin($dlng / 2);
$c = 2 * atan2(sqrt($a), sqrt(1 - $a));

// Distance in KM
$km = round($r * $c, 2);

// Distance in Miles
$miles = round($km * 0.621371192, 2);

echo 'The distance between '.$postcode1.' and '.$postcode2.' is '.$km.'Km ('.$miles.' miles).';

?>

You could use $result1[0] and $result2[0] to check codes. If the value is anything other than 200 the postcode is invalid. Also note UK is also searched for to guarantee correct results!

The result is also rounded to make sure we only have 2 decimal places. Make sure your postcodes do not have any spaces in when they go to Google, if you’re collecting them from a form maybe use:

function nowhitespace($data) {
return preg_replace('/\s/', '', $data);
}
$postcode1 = nowhitespace($postcode1);

to remove all spaces before processing, and the following to check it’s ok after processing:

if (($result1[0] != 200) || ($result2[0] != 200)) {
echo "<p>Invalid Postcode(s) Entered. Please try again.</p>";
} else {

Good luck!