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Retrieve latitude and longitude of a draggable pin via Google Maps API V3

I will explain. I managed to have a draggable pin on a map. I want to retrieve the coordinates of this point and put them into two fields: Latitude and Longitude. These coordinates will later be send to a SQL table via PHP. Here is an example of what I intend to do, but instead of several pins, it's just one and it's draggable. The problem is: I'm not even able to display the coordinates of the initial point. And of course when the user moves the pin, I want the coordinates to change as well in the fields. I hope I made myself clear. What did I do wrong? Should I use the Geocoding service?

Here goes the JS:

<script type="text/javascript">
  var map;
  function initialize() {
  var myLatlng = new google.maps.LatLng(40.713956,-74.006653);

  var myOptions = {
     zoom: 8,
     center: myLatlng,
     mapTypeId: google.maps.MapTypeId.ROADMAP
     }
  map = new google.maps.Map(document.getElementById("map_canvas"), myOptions); 

  var marker = new google.maps.Marker({
  draggable: true,
  position: myLatlng, 
  map: map,
  title: "Your location"
  });

  google.maps.event.addListener(marker,'click',function(overlay,point){
     document.getElementById("latbox").value = lat();
     document.getElementById("lngbox").value = lng();
     });

}
</script> 

And the HTML:

<html>
<body onload="initialize()">

  <div id="map_canvas" style="width:50%; height:50%"></div>

  <div id="latlong">
    <p>Latitude: <input size="20" type="text" id="latbox" name="lat" ></p>
    <p>Longitude: <input size="20" type="text" id="lngbox" name="lng" ></p>
  </div>

</body>
</html>
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by (71.8m points)

Either of these work

google.maps.event.addListener(marker, 'click', function (event) {
    document.getElementById("latbox").value = event.latLng.lat();
    document.getElementById("lngbox").value = event.latLng.lng();
});

google.maps.event.addListener(marker, 'click', function (event) {
    document.getElementById("latbox").value = this.getPosition().lat();
    document.getElementById("lngbox").value = this.getPosition().lng();
});

You might also consider using the dragend event also

google.maps.event.addListener(marker, 'dragend', function (event) {
    document.getElementById("latbox").value = this.getPosition().lat();
    document.getElementById("lngbox").value = this.getPosition().lng();
});

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