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!

After we'll be done with our example, the final result should look more or less like that:

As usually don't forget to include jQuery library in the head section of your document. Let's take a closer look at the jQuery code we will use in this example:

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$(document).ready(function(){
  $('#select').change(function() {
    var option = $(this).val();
    $.get('select.php', {select:option}, function(data) {
      $('#result').html(data).hide().fadeIn(1000);
    });
  });
});

I think I don't need to remind anyone that you should place this code also in the head section of your document. Our goal is to write unobtrusive code though.

Our code is really simple this time. After the DOM is loaded we add an event listener, which will be triggered on onchange event of our drop down list with id select. If the event was triggered we save the value of chosen option in 'option' variable and use the AJAX request to get the content of the remote file, which in our case is select.php, which should be placed in the same directory. Additionally we pass an argument, which in our case is the value of the chosen option. We then use html() to past retrieved data into our div container with id result, we hide it and use fadeIn() effect to display it in a nicer way.

Here is the HTML code you should put in the body section of your document:

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<select name="select" id="select">
	<option value="">Select</option>
	<option value="option1">Option 1</option>
	<option value="option2">Option 2</option>
	<option value="option3">Option 3</option>
	<option value="option4">Option 4</option>
	<option value="option5">Option 5</option>
</select>
<div id="result" style="border:1px solid #000;padding:10px;color:#ff0000;display:none;"></div>

I don't think this code needs any further explanation. Probably, what's more important, is the content of the php file:

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if($_GET['select'] == 'option1') {
  echo 'the option you have chosen is 1';
} elseif($_GET['select'] == 'option2') {
  echo 'the option you have chosen is 2';
} elseif($_GET['select'] == 'option3') {
  echo 'the option you have chosen is 3';
} elseif($_GET['select'] == 'option4') {
  echo 'the option you have chosen is 4';
} elseif($_GET['select'] == 'option5') {
  echo 'the option you have chosen is 5';
}

Basically we display the content according to the data passed in our AJAX request. You can do everything possible with this file, for example get the information from MySQL table. Additionally you can pass more attributes in the AJAX request, which you can get either from hidden input fields or just predefine them in the function.

You can also adjust this function to load contents from remote text files or any other files you can imagine. In the case of text files though, I would name the files using the name attribute of our drop down list, save it in the variable and pass it to the AJAX request as the file name. Have fun with this one.

DEMO PAGE

As usually we need to include our jQuery library in the head of our document. Here is the code I used to accomplish this example:

1. CSS
[source:html]
.navi {
margin:0;
padding:0;
list-style-type:none;
position:absolute;
}
.navi .navi-point {
float:left;
margin:2px;
padding:5px;
border:1px solid #000;
background:#ccc;
width:80px;
}
.sub-navi {
margin:0;
padding:0;
list-style-type:none;
display:none;
}
.link {
cursor:pointer;
}
[/source]

2. jQuery
[source:javascript]
$(document).ready(function(){
$('.navi-point').hover(
function () {
$('.sub-navi',this).slideDown(1000);
},
function () {
$('.sub-navi',this).slideUp(1000);
}
);
});
[/source]

3. HTML
[source:html]

• link1
  • link1.1
  • link1.2
  • link1.3

[/source]
Basically we are triggering our function after the DOM is ready and we are listening until user hovers over one of the span elements with class 'link'. The rest will jQuery do for us. You can replace the slide effect with fade effect, however you will need to change CSS to do that. Of course, if you want that your drop down menu covers the text, which will be displayed beneath it, you need to position it correctly in CSS. Have fun with it.