To see, how our final solution will look like, go here

1. Geo Class - Geo.class.php

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class Geo
{
 
    private $xml;
 
    protected function _init()
    {
        $this->xml = simplexml_load_file('geo.xml', 'SimpleXMLElement');
    }
 
    public function getDropDown($id, $option = array())
    {
        $this->_init();
 
        $select = '<select name="' . $id . '" id="' . $id . '">';
 
        if ($option['include_custom'] != '')
            $select.= '<option value="" selected="selected">' . $option['include_custom'] . '</option>';
 
        foreach ($this->xml->children() as $child) {
            $select.= '<option value="' . $child->name . '">' . $child->name . '</option>';
        }
 
        $select.= '</select>';
 
        return $select;
    }
 
    public function getLocation($identifier)
    {
        $this->_init();
 
        $coordinates = array();
 
        foreach ($this->xml->children() as $child)
            if ($child->name == $identifier) {
                $temp = explode(',', $child->Point->coordinates);
                $coordinates = array(
                                    'lat' => $temp[0],
                                    'lng' => $temp[1]
                );
            }
 
        return $coordinates;
    }
}

It wasn't really necessary to put this functions into a class, but it is just a habit We define a protected function _init(), which we call every time we want to use our KML file to retrieve information out of it. The function simplexml_load_file initializes an SimpleXMLElement object for us, which we can use later. The function getDropDown with the first mandatory argument and the second optional will be responsible for displaying the drop down field for us. I think I don't need to explain it in detail. The last function getLocation will retrieve the latitude and longitude from KML file. So let's move to index.php file, which will be the core of this example.

2. Core file - index.php

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include('Geo.class.php');
$geo = new Geo();

Before we send any headers we include our Geo.class.php file and initialize our Geo class. After that goes the usual tag tags and the google maps and jQuery scripts. In the section of our document goes the actual jQuery part.

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$(document).ready(function() {  
  var mapContainer = $('#map')[0];
  var markerStart;
  var markerEnd;
  if(GBrowserIsCompatible()) {    
    if(mapContainer) {
      var map = new GMap2(mapContainer);
      map.addControl(new GLargeMapControl);  
      map.setCenter(new GLatLng(52.519015140666,13.419671058654785), 14);
 
      $('#start').change(function() {
        var location = $(this).val();
 
        if (location == '')
          return;
 
        $.getJSON('helper.php', { location: location }, function(data) {
          if (markerStart)
            map.removeOverlay(markerStart);
 
          pointA = new GLatLng(data.lat, data.lng);
          markerStart = new GMarker(pointA);
          map.addOverlay(markerStart);
        });
      });
 
      $('#end').change(function() {
        var location = $(this).val();
 
        if (location == '')
          return;
 
        $.getJSON('helper.php', { location: location }, function(data) {
          if (markerEnd)
            map.removeOverlay(markerEnd);
 
          var blueIcon = new GIcon(G_DEFAULT_ICON);
          blueIcon.image = "http://gmaps-samples.googlecode.com/svn/trunk/markers/blue/blank.png";
          var markerEndOptions = { icon: blueIcon };
 
          pointB = new GLatLng(data.lat, data.lng);
          markerEnd = new GMarker(pointB, markerEndOptions);
          map.addOverlay(markerEnd);
        });
      });
 
      $('#submit').click(function() {
        if (window.pointA === undefined || window.pointB === undefined) {
          alert("You need to choose start and end");
          return;
        }
 
        var directions = new GDirections(map);
        route = Array(pointA, pointB);
 
        GEvent.addListener(directions, 'load', function() {
          var dist = directions.getDistance().html;
          $('#distance').html(dist);
        });
 
        directions.loadFromWaypoints(route);
      });
    }
  }
});

Maybe it is long but pretty straight forward. As you can read in my other examples, we first initialize jQuery, so it starts after our document is loaded. After that we define our map container and our markers. After we check if our browser is compatible and our map container exists, we initialize the map with couple options (large controls, zoom level = 14 and the center of the map).

We add two event listeners, which are triggered on onchange event of our drop downs (with id start and end respectively, the html code will follow). If you use the $option parameter in getDropDown function for displaying custom blank option, we check if the user chose this option and return false if he did. If he chose a valid option, we use an AJAX request and retrieve the geolocation from our helper file.

After our call returns some data, we check, if we have already any markers saved in our map and if we do, we first remove them and then place a new marker according to the option chosen in the drop down.

We repeat the same for the drop down with id 'end'. Actually we could have put this two events into a separate function, but to make this example clear I purposely didn't do that.

The last event listener is triggered, when a user clicks on a 'calculate route' button. First we check, if both points were placed by the user, and if not we display an alert, that he or she has to provide valid starting and ending point. This check might not work in IE, therefore you might need to do some changes, so it also works in IE.

We initialize GDirections Class and define our route with starting and ending point. I also use the getDistance method to display the amount of kilometers between this two points. As the last thing we need to do is to display the directions on the map and voila, we are done

What we still need it the rest of index.php file and our helper, and KML file.

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<div id="navigation">
        Start <?php echo $geo->getDropDown('start', array('include_custom' => 'please choose...')); ?>
        Stop <?php echo $geo->getDropDown('end', array('include_custom' => 'please choose...')); ?>
        <input type="button" name="submit" id="submit" value="calculate route" />
</div>
<div id="distance"></div>
<div id="map" style="width: 1000px; height: 600px;"></div>

Pretty straight forward. We display our navigation with an empty option 'please choose...', the 'calculate route' button and containers for distance and map.

3. Our helper - helper.php

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include('Geo.class.php');
$geo = new Geo();
echo json_encode($geo->getLocation($_GET['location']));

Pretty simple, isn't it Just initialize the class and call the method to retrieve location with the location argument used in the _GET request.

4. KML file - geo.xml

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<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.2">
  <Placemark>
    <name>Alexanderplatz</name>
    <description>Center of Berlin</description>
    <Point>
      <coordinates>52.52238370531909,13.409671783447266</coordinates>
    </Point>
  </Placemark>
  <Placemark>
    <name>Frankfurter Tor</name>
    <description>A nice place to live</description>
    <Point>
      <coordinates>52.51595970749194,13.4527587890625</coordinates>
    </Point>
  </Placemark>
  <Placemark>
    <name>Warschauerstr.</name>
    <description>Place to go and spend some time with friends</description>
    <Point>
      <coordinates>52.508568336719854,13.451085090637207</coordinates>
    </Point>
  </Placemark>
  <Placemark>
    <name>Revelerstr.</name>
    <description>Cassiopeia Club</description>
    <Point>
      <coordinates>52.50721006978328,13.457050323486328</coordinates>
    </Point>
  </Placemark>
  <Placemark>
    <name>Frankfurter Allee</name>
    <description>Shopping Center</description>
    <Point>
      <coordinates>52.513818166144006,13.474087715148926</coordinates>
    </Point>
  </Placemark>
</kml>

It is a file I prepared by myself. As far as I know, you can create them using the Google Earth application. Probably they can be way more complex than this one. But I guess it will be a nice subject for next example Good luck with this one and as usually, in case of any question, you know how to find me. Cheers!

The first thing you need to do is to go to getpos.de and register a new account. Unfortunately this service is only in German, but I don't think you should have any problem with registering a new account. Let's take a look at our class:
[source:php]
class Geolocation {

private $ip;
private $xml_data;
private $xml;

public $geo;
public $error;

function __construct($ip) {
$this->ip = $ip;
$this->xml_data = simplexml_load_file("http://services.getpos.de/ip2loc.asmx/GetIPPosition?UserName=YOUR_USERNAME&Password=YOUR_PASSWORD&IPAddress=".$this->ip);
}

public function findGeo() {
if(!$this->xml_data) {
$this->error = "service unavailable";
return false;
}
$this->xml = new SimpleXMLElement($this->xml_data);
$this->RecurseXML($this->xml,$this->geo);
}

private function RecurseXML($xml,$vals,$parent=""){
$child_count = 0;
foreach($xml as $key=>$value) {
$child_count++;
$k = ($parent == "") ? (string)$key : $parent.".".(string)$key;

if($this->RecurseXML($value,$this->geo,$k) == 0)
$this->geo[$k] = (string)$value;
}
return $child_count;
}
}
[/source]
We define IP address, XML data and an instance of SimpleXMLObject as private properties and our error handler and actual geo data as public properties. In our constructor we pass IP address and we use simplexml_load_file function to interpret the XML file into an object. Obviously you need to replace YOUR_USERNAME and YOUR_PASSWORD with the information you will use to register at getpos.de. In findGeo() method we first check, if the service is available, and if not we show error message. If our service is available though, we instantiate SimpleXMLObject with the XML data. We than use RecurseXML() method to translate our object into a suitable array. The credit for RecurseXML() goes to transglobe at gmx dot de. I found this function in the comments section of PHP manual and changed it a little bit to suit our needs.

Let's take a closer look, how to use our class:
[source:php]
include("geolocation.class.php");
$geo = new Geolocation($_SERVER['REMOTE_ADDR']);

$geo->findGeo();
echo (isset($geo->error)) ? $geo->error : '';

echo "geo['returncode']:".$geo->geo['returncode']."
";
echo "geo['country.code']:".$geo->geo['country.code']."
";
echo "geo['country.name']:".$geo->geo['country.name']."
";
echo "geo['region.code']:".$geo->geo['region.code']."
";
echo "geo['region.name']:".$geo->geo['region.name']."
";
echo "geo['city']:".$geo->geo['city']."
";
echo "geo['position.longitude']:".$geo->geo['position.longitude']."
";
echo "geo['position.latitude']:".$geo->geo['position.latitude']."
";
echo "geo['returncode']:".$geo->geo['returncode']."
";
[/source]
We include our class and instantiate it with the remote address of a visitor. We than call findGeo() method, which will translate the IP address for us. We can than echo our results or just use them to display relevant information for our users. Obviously, if a user is connected through a proxy or some AOL users in Europe, who are connected through American servers, this class wont retrieve correct information. You need to take into consideration though, that about 65% of your visitors will get correct content. I hope it is clear enough. If you encounter any problems with this class please let me know. As mentioned before, it would be also nice if you could give me any feedback about the accuracy of this service.

private $url = array();

}
[/source]
We define private array url, in which we will store URLs prepared for cURL request. Let's build a contructor.
[source:php]
class Geolocation {

private $url = array();

function __construct($file) {
$gmapkey = "YOURKEY";
$address = file($file);
foreach($address as $addres) {
$this->url[] = "http://maps.google.com/maps/geo?q=".urlencode($addres)."&output=csv&key=".$gmapkey;
}
}
}
[/source]
You need to replace $gmapkey with the key you can sign for at google. Our __constructor reads the text file and saves each line in an array. We then loop through this array and initialize URLs.

In the next method we will loop through the addresses to retrieve the geolocation.

[source:php]
class Geolocation {

private $url = array();

function __construct($file) {
$gmapkey = "YOURKEY";
$address = file($file);
foreach($address as $addres) {
$this->url[] = "http://maps.google.com/maps/geo?q=".urlencode($addres)."&output=csv&key=".$gmapkey;
}
}
public function getLatLng() {
$i=1;
foreach($this->url as $urls) {
$cinit = curl_init();
curl_setopt($cinit, CURLOPT_URL, $urls);
curl_setopt($cinit, CURLOPT_HEADER,0);
curl_setopt($cinit, CURLOPT_USERAGENT, $_SERVER["HTTP_USER_AGENT"]);
curl_setopt($cinit, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($cinit, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec($cinit);
curl_close($cinit);

if(strstr($data,"200")) {
$data = explode(",",$data);
echo $i.": ";
$zoom = $data[1];
echo $lat = $data[2];
echo $lon = $data[3]."
";
}

/*
$sql = "INSERT INTO..."
$res = mysql_query($sql);
echo ($res) ? $i.": lat:".$latitude." lon: ".$longitdue." -- OK
" : $i.": ERROR
";
*/
$i++;
}
}
}
[/source]
You can either echo the results or just save them in your MySQL database. You can also make multidimensional array and save some extra information about the certain place.

Let's take a look at how you should use this class.
[source:php]
include('geolocation.class.php');
$geo = new Geolocation('address.txt');
$geo->getLatLng();
[/source]
Basically you need to include the class, initialize it with the name of the file you want to use and getLatLng will do the magic for you. This class is pretty old and you may encounter one problem using it. After 10th request I started to receive the same geolocation for different places. What you can do is to put the foreach loop to sleep for 2 seconds and it should be fine. That's why I actually use iterator in this function. You basically need to add this line right after the loop starts.
[source:php]
if($i%10 == 0) sleep(2);
[/source]

Here is the content of the text file:
[source:html]
Berlin, Dieffenbachstr. 38
Berlin, Cuvrystr. 32
Berlin, Lasdehner Str. 30
[/source]
Basically one address per line. That would be all, have fun with playing and extending this class.