Google HTTP Geocoding

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I have been doing a lot of searching in regards to Google Maps and information on there API. In my Addressbook I had a some what dynamic but clumsy way of showing some ones location.

So when I would pull the information I would use a PHP function called “urlencode” it basically converts spaces to underscores so your URL won’t explode and make Google angry.

This works fine but I was opening a new window that I had no control over. so that’s when I began to look into the API and after a bit of looking I found that they had support for HTTP Request and by doing so Google spits out a bit of XML.

The basic URL looks like this:

http://maps.google.com/maps/geo?q=address,+city,+state&output=xml&key=abcdefg

Using + to replace spaces and, to signal the next field.

Click to see output example

There were a few options for output “xml, kml, csv, or json” and after a bit of research i chose XML. Something i haven’t had a lot of experience to work with.

In my application I have all the addresses saved in a Database and need to save the Latitude and Longitude so using the same method as my past example i used the “urlencode” function to make my addresses safe for the URL.

   $googleAddress = "http://maps.google.com/maps/geo?q=".urlencode($address) .'+'. urlencode($city) .'+'. urlencode($province).'+'. urlencode($country)."&output=xml&key=$key";

The next task was to get the contents of the file so I used the “file_get_contents” function and passed it my URL

   $googlePage = file_get_contents($googleAddress);

This is where I had some learning to do, after the XML was opened I had to gather the properties. I used the “SimpleXMLElement” function to convert XML to an object that can be processed with normal property selector.

Note: The SimpleXMLElement will only work in PHP 5+

$xml = new SimpleXMLElement($googlePage);

Now that we have the values from the XML we can assign variables to them that will allow us to display the results.

http://ca.php.net/xml

list($lng, $lat, $altitude) = explode(",",
     $xml->Response->Placemark->Point->coordinates);

All that is left to do is display the results, at this point you could also use the information and store it in a database as i did for my Addressbook.

echo "Longitude: $longitude, Latitude: $latitude";

Full Code:

   // API Key
   $key=""

   // Google Geo Address
   $googleAddress = "http://maps.google.com/maps/geo?q=".urlencode($address) .'+'. urlencode($city) .'+'. urlencode($province).'+'. urlencode($country)."&output=xml&key=$key";

   // Retrieve the URL contents
   $googlePage = file_get_contents($googleAddress);

   // Parse the returned XML file
   $xml = new SimpleXMLElement($googlePage);

   // Parse the coordinate string
list($lng, $lat, $altitude) = explode(",",
     $xml->Response->Placemark->Point->coordinates);

// Output the coordinates
echo "Longitude: $longitude, Latitude: $latitude";

That’s about it on this subject; there are many ways to Geocode and this is just one of them.

Links:
Google Geocoding HTTP Request