How to get Locations in a 50 Mile Radius with Google Maps API v.3

In this post, I will demonstrate how to make getting locations within a given radius simple. In order to make everyone understand, I will break it down into smaller, easy to read steps.

The Distance-Matrix

The key to creating a solution that gets all locations within a given distance radius is to use the Google Maps API Distance-Matrix. Let's examine a simple example request to the Distance-Matrix Json API:

Single Destination URL Example:

https://maps.googleapis.com/maps/api/distancematrix/json?units=imperial&origins=44311&destinations=45735&key=Your_API_Key

copy and paste the above URL into a web browser and replace the text, Your_API_Key, with your google Maps V.3 API key. If you don't have an API key yet, they are surprisingly easy to obtain from https://developers.google.com/maps/web-services/

The Response:

The URL above will return a Json response of:

{
   "destination_addresses" : [ "Guysville, OH 45735, USA" ],
   "origin_addresses" : [ "Akron, OH 44311, USA" ],
   "rows" : [
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "166 mi",
                  "value" : 267653
               },
               "duration" : {
                  "text" : "2 hours 30 mins",
                  "value" : 8989
               },
               "status" : "OK"
            }
         ]
      }
   ],
   "status" : "OK"
}

Notice that I only used zip codes for orgin and destination in my example URL. You can use any acceptable address format instead of just a zip code of you like, but I find that for getting distances, zip codes work quite efficiently. Examples of acceptable addresses include:

  • Cleveland, OH
  • 593 Brown Street, Akron, Ohio
  • 44319
  • Akron, Ohio 4319
  • 593 Brown Street, Akron, Ohio 44311
  • USA
  • Amsterdam

Those are just a few acceptable addresses that could be used for either the destination or orgin parameters in the URL used for an API request to the Distance-Matrix.

 

Multiple Destination URL Example:

One thing that's important to know about the Distance-Matrix API is that there are limits on it's free usage. At the time of writing this post, the limits were 2500 elements per day. A single request may take up several elements however, so be careful. However it is much more practical to include several destination addresses in a single request because it will make your script run significantly quicker. Here is a simple example that will return a response with two destination distances using just zip codes for addresses again:

https://maps.googleapis.com/maps/api/distancematrix/json?units=imperial&origins=44311&destinations=45735|44319&key=Your_API_Key

This the json response will include the distances for both zip codes or addresses passed in the URL. Here is the response from the above URL with two destinations:

{
   "destination_addresses" : [ "Guysville, OH 45735, USA", "Akron, OH 44319, USA" ],
   "origin_addresses" : [ "Akron, OH 44311, USA" ],
   "rows" : [
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "166 mi",
                  "value" : 267653
               },
               "duration" : {
                  "text" : "2 hours 30 mins",
                  "value" : 8989
               },
               "status" : "OK"
            },
            {
               "distance" : {
                  "text" : "8.9 mi",
                  "value" : 14385
               },
               "duration" : {
                  "text" : "14 mins",
                  "value" : 836
               },
               "status" : "OK"
            }
         ]
      }
   ],
   "status" : "OK"
}

Parsing Json data with PHP

The next task is to fetch a response from PHP and parse the Json data in your PHP code. Lets look at a practical example using our first URL example above that has a single zip code as the destination address and also a single zip code for the orgin. Here is the PHP code to make the request, get a Json response and parse the distance from that response:

<?php
$url = "https://maps.googleapis.com/maps/api/distancematrix/json?units=imperial&origins=44311&destinations=45735&key=Your-API-Key";

    //fetch json response from googleapis.com:
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $response = json_decode(curl_exec($ch), true);
    //If google responds with a status of OK
    //Extract the distance text:
    if($response['status'] == "OK"){
        $dist = $response['rows'][0]['elements'][0]['distance']['text'];
        echo "<p>Dist: $dist</p>";
    }
?>

Now lets have a look at how we would modify the above code for a request with two destination addresses instead of one:

<?php
$url = "https://maps.googleapis.com/maps/api/distancematrix/json?units=imperial&origins=44311&destinations=45735|44319&key=Your-API-Key";

    //fetch json response from googleapis.com:
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $response = json_decode(curl_exec($ch), true);
    //If google responds with a status of OK
    //Extract the distance text:
    if($response['status'] == "OK"){
        $dist = $response['rows'][0]['elements'][0]['distance']['text'];
        echo "<p>Dist: $dist</p>";
        $dist2 = $response['rows'][0]['elements'][1]['distance']['text'];
        echo "<p>Dist2: $dist2</p>";
    }
?>

If you insert your own API key in the above code and run it from your own server, the response would look like this:

Dist: 166 mi

Dist2: 8.9 mi

Notice the difference in the $dist and $dist2 variable values. The key of the elements is different. The first distance is stored in elements[0] while the second is stored in elements[1]. If we had three destinations in the request, the third would be in elements[2] and so on...

How to figure out the values

So, what if you want more than just distance from the returned json element? Lets examine the returned data and figure out how to get it into PHP variables. In the example code above, try placeing this code right after the line that reads "if($response['status'] == "OK"){" and it will show you what the PHP array looks like after the Json response was converted to a PHP object:

        echo "<pre>";
        print_r($response);
        echo "</pre>";

The above code inserted into the last code example would look like:

<?php
$url = "https://maps.googleapis.com/maps/api/distancematrix/json?units=imperial&origins=44311&destinations=45735|44319&key=Your-API-Key";

    //fetch json response from googleapis.com:
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $response = json_decode(curl_exec($ch), true);
    //If google responds with a status of OK
    //Extract the distance text:
    if($response['status'] == "OK"){
        echo "<pre>";
        print_r($response);
        echo "</pre>";
        $dist = $response['rows'][0]['elements'][0]['distance']['text'];
        echo "<p>Dist: $dist</p>";
        $dist2 = $response['rows'][0]['elements'][1]['distance']['text'];
        echo "<p>Dist2: $dist2</p>";
    }
?>

Again, replace "Your-API-Key" in the URL variable with your own key and run the code. You should see results like this:

Array
(
    [destination_addresses] => Array
        (
            [0] => Guysville, OH 45735, USA
            [1] => Akron, OH 44319, USA
        )

    [origin_addresses] => Array
        (
            [0] => Akron, OH 44311, USA
        )

    [rows] => Array
        (
            [0] => Array
                (
                    [elements] => Array
                        (
                            [0] => Array
                                (
                                    [distance] => Array
                                        (
                                            [text] => 166 mi
                                            [value] => 267653
                                        )

                                    [duration] => Array
                                        (
                                            [text] => 2 hours 30 mins
                                            [value] => 8989
                                        )

                                    [status] => OK
                                )

                            [1] => Array
                                (
                                    [distance] => Array
                                        (
                                            [text] => 8.9 mi
                                            [value] => 14385
                                        )

                                    [duration] => Array
                                        (
                                            [text] => 14 mins
                                            [value] => 836
                                        )

                                    [status] => OK
                                )

                        )

                )

        )

    [status] => OK
)

Dist: 166 mi

Dist2: 8.9 mi

First you see the array printed out from the response after it's converted from Json to a PHP array, then you see the two distances printed to the screen in the last two lines. Examine the array closely and you can figure out the correct keys to use to pick out specific values from the array in your PHP code.

More info on the Distance-Matrix can be found at https://developers.google.com/maps/documentation/distance-matrix/start

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