Calculate the distance between two locations using PHP

In this article, we introduce a simple example to calculate the distance between two locations using PHP and google map API. We can easily get the latitude and longitude of both source and destination addresses in JSON format by sending request to google map geocode api. The distance calculation is helpful when your web application works with the user's location. The Google Maps Geocoding API helps to easily calculate the distance between two locations from latitude and longitude in kilometers or miles.

This is the main file, that we will call on the browser. This file contains two input boxes to enter source and destination addresses and a selection option to select the unit.

When the user clicks on the submit button, getRouteDistance() method will be called. This function calls the google api and gets the latitude and longitude of the entered addresses from json_encode and calculates the distance between them.

The getRouteDistance() function accepts three parameters -

$source_adrs - Required, Source address.
$dest_adrs - Required, Destination address.
$unit - Optional, The default unit is miles.

To use the Google Maps Geocoding API, you need to specify the API Key in your request. Before getting started, go to Google Cloud Platform Console for Geocoding API and generate an API key.

index.php

<!DOCTYPE html>
<html>
   <head>
       <title>Calculate the distance between two locations</title>
       <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" >
       <style type="text/css">
            .formbg { background-color: #66CCFF; padding: 10px 0 10px 20px; color: #191919;
                    border-radius: 10px;  border: 2px solid #6D0839; width: 780px; margin: 0 auto;
            }
	   label { font-size: 18px; }
	   h1 {color: #003366;}
       </style>
   </head>

   <body>
      <?php 
      function getRouteDistance($source_adrs, $dest_adrs, $unit){

          // Your API Key
          $apiKey = 'Your_Google_API_Key';

          //Send request and receive json data
          // Geocoding API request with source address
          $s_geocode = file_get_contents('http://maps.google.com/maps/api/geocode/json?address='.$source_adrs.'&sensor=false&key='.$apiKey');
          $s_latlong = json_decode($s_geocode);

          // Geocoding API request with destinationaddress
          $d_geocode = file_get_contents('http://maps.google.com/maps/api/geocode/json?address='.$dest_adrs.'&sensor=false&key='.$apiKey');
          $d_latlong = json_decode($d_geocode);

          //Get latitude and longitude
          $lat1 = $s_latlong->results[0]->geometry->location->lat;
          $long1 = $s_latlong->results[0]->geometry->location->lng;
          $lat2 = $d_latlong->results[0]->geometry->location->lat;
          $long2 = $d_latlong->results[0]->geometry->location->lng;

          //Calculate the distance from latitude and longitude
          $theta = $long1 - $long2;
          $dist = sin(deg2rad($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);

          // Convert unit and return distance
          if ($unit == "K") {
              return ($miles * 1.609344).' KM';
          } else {
              return $miles.' MI';
          }
      } 
      ?>
      <div class="form-group row formbg">
          <?php

          // display the distance between locations on web page
          if(($_POST['source'] != '') && ($_POST['destination'] != '')) {
              $source = $_POST['source'];
              $destination = $_POST['destination'];
              $unit = $_POST['unit'];
              $source_adrs = str_replace(' ', '+', $source);
              $dest_adrs = str_replace(' ', '+', $destination);
              $distance = getRouteDistance($source_adrs, $dest_adrs, $unit);
              if($distance != '') {
                echo 'Distance Between <b>'.$source.'</b> and <b>'.$destination.' : </b><b>'.$distance.'</b>'
                    .'<br/><br/>';
              }
          }
          ?>

          <form action="" method="post">
             <div class="form-group row">
                <label class="col-xs-3 col-form-label">Enter Source Address: </label>
                <div class="col-xs-5">
                 <input class="form-control" type="text" name="source" value="" placeholder="Source">
                </div>
             </div>
             <div class="form-group row">
                <label class="col-xs-3 col-form-label">Enter Destination Address: </label>
                <div class="col-sm-5">
                 <input class="form-control" type="text" name="destination" value="" placeholder="Destination">
                </div>
              </div>
              <div class="form-group row">
                 <label class="col-xs-3 col-form-label">Unit: </label>
                 <div class="col-sm-5">
                  <select name="unit" class="form-control">
                      <option value="k">Kilometer</option>
                      <option value="m">Mile</option>
                  </select>
              </div>
             </div>
             <div class="form-group row">
                 <label class="col-xs-3 col-form-label"> </label>
                  <div class="col-sm-5">
                   <input class="btn btn-primary" type="submit" value="Submit"/>
                  </div>
                </div>
          </form>
      </div>
 </body>
</html>

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