This Saturday was the second annual Redline Challenge which is a bar crawl from Downtown Crossing to Davis Square that loosely tracks the MBTA Redline.

This year, we decided to use Foursquare to allow the website to track the position of several of the participants on the challenge. Foursquare natively allows you to track your checkin history with private URLs. Currently, they support a handful of formats with KML being the most interesting for our purposes. You can find your private URLs by navigating to http://foursquare.com/feeds/

We used the Google Maps API along with the KML stream from Foursquare to dynamically place markers on the map as different users checked in to different venues.

Here is the PHP we used to pull back the KML feed, transform it to JSON, and spit it back to our jQuery on the client side:

$xml = simplexml_load_file( "http://feeds.foursquare.com/history/myurl.kml" );
$arr["a"] = $xml->Folder;
$xml = simplexml_load_file( "http://feeds.foursquare.com/history/ackleysurl.kml" );
$arr["m"] = $xml->Folder;

echo json_encode( $arr );

Pretty straight forward. Here is the jQuery code on the client side to add markers to the map:

       $.getJSON( "location.php", {}, function(data){

    	   data.a.Placemark = data.a.Placemark.reverse();

         var hasStarted = false;
         var barIndex = 1;

         $.each( data.a.Placemark, function(i, val){

               if( val.published.indexOf("Sat, 11") == -1 ){
                    return true;
               }

               if( !hasStarted && val.name == "Setfive Consulting" ){
                  hasStarted = true;
               }else if( !hasStarted ){
                  return true;
               }

               var latLng = val.Point["coordinates"].split(",");

               var point = new GLatLng( latLng[1], latLng[0] );

               var marker = new GMarker(point);

               marker.bindInfoWindowHtml( "
"
                                             + barIndex + ". " + val.name + "
Get Directions

" );
               map.addOverlay(marker);

               latLngList.push( point );

               if( i == data.a.Placemark.length-1 ){
            	   map.setCenter(point, 14);
                   $(marker).click();

                   marker.openInfoWindowHtml( "
We are at "
                		                      + barIndex + ". " + val.name
                                              + "
Get Directions

" );

               }

               barIndex++;

           });
           var polyline = new GPolyline( latLngList, "#ff0000", 5 );
           map.addOverlay(polyline);

         latLngList = [];
         data.m.Placemark = data.m.Placemark.reverse();

        var blueIcon = new GIcon(G_DEFAULT_ICON);
        blueIcon.image = "http://www.google.com/intl/en_us/mapfiles/ms/micons/blue-dot.png";
        markerOptions = { icon:blueIcon };

        barIndex = 1;

        $.each( data.m.Placemark, function(i, val){

               if( val.published.indexOf("Sat, 11") == -1 ){
                    return true;
               }

               var latLng = val.Point["coordinates"].split(",");

               var point = new GLatLng( latLng[1], latLng[0] );

               var marker = new GMarker(point, markerOptions);

               marker.bindInfoWindowHtml( "
"
                                             + barIndex + ". " + val.name + "
Get Directions

" );
               map.addOverlay(marker);

               barIndex++;

               latLngList.push( point );

           });
           var polyline = new GPolyline( latLngList, "#001299", 5 );
           map.addOverlay(polyline);

       })

That’s about it.

So we decided to use the Google Calendar API in one of our applications to allow users to easily view and export events from outside the app. In general, the API was working well – I was using the Zend library to interact with Google and things seemed fine.

That was until I tried to embed the calendar using Google’s iframe embed code. For some reason, events weren’t showing up in the embeded iframe calendar even though they were showing up in the actual calendar on calendar.google.com. Even stranger, the events were present in a JSON object on the embeded page and they were showing up in the RSS feed for the calendar.

After literally days of debugging and experimenting I finally found out the culprit.

For some reason, events created via the API that start and end at exactly the same time – say a start date of 08-05-2009 10:00:00 and an end date of 08-05-2009 10:00:00 don’t render on the embeded iframe calendar.

What is even more bizarre is that if you create an event via the web interface that starts and ends at the same time, it will render correctly on an embeded calendar.

Anyway, that was weird. All the events without explicit start and end times now last a grand total of one minute.

PS. Kudos to Daum for finding a constant for PHP’s date() function to generate RFC3339 timestamps.

Use like so:

  $date = date(DATE_RFC3339, $timestamp);

To get back a valid RFC3339 for the Google Calendar API.

A few months ago we integrated Google calendar into an application that we built for a client. Anyway, today I sat down to customize which calendars certain events were being created on. We’re using the Zend Framework’s GData package to interact with Google Calendar and surprisingly the documentation is pretty lacking.

Specifically, I was looking to create events on a calendar that was not the “primary” calendar for a user. After poking around and experimenting, I finally got things to work.

First, you can retrieve the list of available calendars with:

$service = Zend_Gdata_Calendar::AUTH_SERVICE_NAME;
$user = sfConfig::get("app_gcal_user");
$pass = sfConfig::get("app_gcal_password");

$client = Zend_Gdata_ClientLogin::getHttpClient($user, $pass, $service);
self::$service = new Zend_Gdata_Calendar($client);
$calFeed = self::$service->getCalendarListFeed();

$arr = array();
foreach ($calFeed as $calendar) {
  $arr[] = array( “title” => $calendar->title->text, “uri” => $calendar->getEditLink(“alternate")->href   );
}

Next, when creating the events pass in the uri and the events will appear on the alternate calendar.

self::$service->insertEvent($event, $arr[1][“uri”]);