Google GeoCoding from PHP with Curl & JSON

GeoCoding is the process of converting an address into a latitude and longitude. Google provides a Geocoding API that you can access from PHP. Here's how you do it:

$a = urlencode($addr);
   $geocodeURL = 
   "http://maps.googleapis.com/maps/api/geocode/json?address=$a&sensor=false";
   $ch = curl_init($geocodeURL);
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
   $result = curl_exec($ch);
   $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
   curl_close($ch);
   if ($httpCode == 200) {
      $geocode = json_decode($result);
      $lat = $geocode->results[0]->geometry->location->lat;
      $lng = $geocode->results[0]->geometry->location->lng; 
      $formatted_address = $geocode->results[0]->formatted_address;
      $geo_status = $geocode->status;
      $location_type = $geocode->results[0]->geometry->location_type;
   } else {
     $geo_status = "HTTP_FAIL_$httpCode";
   }

Let's break it down a few lines at a time. First you want to build the URL with the address encoded using PHP's urlencode() function. This makes sure that no unsavory characters appear within the URL. In the words of the PHP manual, urlencode():

Returns a string in which all non-alphanumeric characters except -_. have been replaced with a percent (%) sign followed by two hex digits and spaces encoded as plus (+) signs.

Note that the URL also specifies the format we want Google to use for the results. In this case the "/json" part of the URL says we want results returned in JSON format (the other option is XML).

$a = urlencode($addr);
$geocodeURL = "http://maps.googleapis.com/maps/api/geocode/json?address=$a&sensor=false";

Now we setup CURL. We initialize it with the URL, and then set the "return transfer" option. This option basically says, to return the results into a PHP variable rather than putting them in a file on the disk.

$ch = curl_init($geocodeURL);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

Now we tell CURL to do it's thing, and check the result. When we call curl_exec(), it opens an HTTP connection to the URL we specified and performs an HTTP GET, returning the results into the $result variable. The call to cur_getinfo() returns the HTTP response code. If everything worked, it should be 200.:

$result = curl_exec($ch);
$httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);

In the success case, we decode the JSON string which is stored in the $result variable, then pull some of the data out of it. Note that if everything went well on Google's end, then $geo_status should get set to "OK".

if ($httpCode == 200) {
      $geocode = json_decode($result);
      $lat = $geocode->results[0]->geometry->location->lat;
      $lng = $geocode->results[0]->geometry->location->lng; 
      $formatted_address = $geocode->results[0]->formatted_address;
      $geo_status = $geocode->status;
      $location_type = $geocode->results[0]->geometry->location_type;

Finally, we handle the failure case, where the HTTP response code was not 200. Here we just set $geo_status to something that will tell us there was a HTTP failure, and record the response code:

} else {
     $geo_status = "HTTP_FAIL_$httpCode";
   }

At this point you could store the data into a database record. When you go to actually use the data, be sure to check $geo_status to make sure it is set to "OK". In other words, don't assume lat and lng are set correctly, unless $geo_status is "OK".

Finally, note that there are a number of fields returned by Google. For a full description of the API, see the Google Geocoding API documentation. Happy geocoding!

JAVASCRIPT EQUIVALENT?

The code is exactly what you've been looking for, except that it is in php. You are wondering if there's a javascript equivalent of the above code.

Geocoding from Javascript is a good thing to do since the requests will be sent to Google from many different client IP addresses, rather than the address of your server. That way you avoid running into the daily limits Google places on requests from the same IP address.

Google has an example of geocoding from Javascript here.