Google-calendar – Track new events someone else created in a shared Google calendar via email or notification

So you can grab the embed code from the html link in the share settings and splice them together manually. I needed this and just now experimented and it works. There are four parts to a public calendar link.

So they are all like this

1. "https://google.com/calendar/"
2. embed type + "?"
3. "src=" + unique string/name
4. "&ctz=" + timezone string (optional)

And it turns out you can add "&src=UNIQUESTRING" an often as you like. So making sure that either your calendars are wide open, showing free/busy or you are sharing with someone who has been given permission to the calendar in your share settings.

The title for the page is pulled from the first calendar in your src string. And all the colors are the same so you can't tell which calendar is which.

Embed

determines the embed type.

htmlembed embed src= a unique string like this one for NCAA UK basketball schedule

src=ncaab_292_%254bentucky%2B%2557ildcats%23sports%40group.v.calendar.google.com

&ctz= I assume it is for current time zone. Sets your timezone offset

&ctz=America/New_York

So here is a link to a combination of UofK basketball,Jewish Holidays, a home maintenance calendar and a local hackerspace in my hometown.

https://www.google.com/calendar/htmlembed?src=1n5qvjga6i4t6lde35vq5dg8ds%40group.calendar.google.com&src=9fjf6vkf1ou50j2umnju2lnrss%40group.calendar.google.com&src=en.jewish%23holiday%40group.v.calendar.google.com&src=ncaab_292_%254bentucky%2B%2557ildcats%23sports%40group.v.calendar.google.com&ctz=America/New_York

I've solved this with a little help from my friends and iCalcreator. Code as follows:

<?php
/*
To begin with, you will need an access token. This is complicated stuff - getting a regular one is easy, but we want one that lasts permanently. As described in Scenario 5 here: https://developers.facebook.com/roadmap/offline-access-removal/ , we need to:

1. Get a regular short-lived access token
2. Exchange it for a long-lived access token
3. Using our new access token, get a permanent page access token.

First, create a new Facebook app at https://developers.facebook.com/apps/ . It can be named whatever, it's not going to be really used. Fill in a domain - it doesn't matter which, just take one that shows simple HTML and doesn't do any redirects: I used my own static web page, http://jobjorn.se/ , but http://example.org/ may work too.

As instructed by MPaulo on Stack Overflow here: https://stackoverflow.com/a/11238327/564628 , use the app id - from your newly created app - and visit this page:
https://www.facebook.com/dialog/oauth?client_id=MY_APP_ID&redirect_uri=MY_SITE_URL&scope=manage_pages&response_type=token
Be sure to replace "MY_APP_ID" and "MY_SITE_URL".

Then, exchange your short-lived access token for a long-lived access token by visiting this page:
https://graph.facebook.com/oauth/access_token?client_id=MY_APP_ID&client_secret=MY_APP_SECRET&grant_type=fb_exchange_token&fb_exchange_token=YOUR_ACCESS_TOKEN
Be sure to replace "MY_APP_ID", "MY_APP_SECRET", and "YOUR_ACCESS_TOKEN" (the last being the access token you received from the first page)

Finally, get your page access token here:
https://graph.facebook.com/me/accounts?access_token=YOUR_NEW_ACCESS_TOKEN
Be sure to replace "YOUR_NEW_ACCESS_TOKEN" (the access token you recieved from the second page)

Paste it below. It should be permanent, but due to a bug it might only last two months - see https://developers.facebook.com/bugs/151056591697025 for details. It seems to have been fixed however. You can test it here: https://developers.facebook.com/tools/debug/access_token
*/

// You will need to edit these variables.
$access_token = "";
$page = "";

// We don't want to query the Facebook Graph API over and over, so we'll cache our results. You can force the cache to update by visiting the script and appending "?f=true", otherwise it will only run (rather than display the cache) if the cache is older than 3600 seconds (one hour).
$cache = $page . ".cache";
$f = false;
if($_GET['f'] == "true"){
    $f = true;
}
if(!file_exists($cache) || filemtime($cache) <= time()-3600 || $f){

    // Get and decode the data - your page's event list - from the API
    $graph_url = "https://graph.facebook.com/" . $page . "/events?access_token=" . $access_token;
    $data = file_get_contents($graph_url);
    $data = json_decode($data);

    if(!empty($data->error)){
        echo '<b>$data error</b><br />';
        echo $data->error->type . " error (" . $data->error->code . "/" . $data->error->error_subcode . "): " . $data->error->message;
        exit;
    }

    // Go through the list of events, and get and decode more detailed information on each event.
    foreach ($data->data as $event){
        $event_data = file_get_contents("https://graph.facebook.com/" . $event->id . "?access_token=" . $access_token);
        $event_data = json_decode($event_data);

        if(!empty($event_data->error)){
            echo '<b>$event_data error</b><br />';
            echo $event_data->error->type . " error (" . $event_data->error->code . "/" . $event_data->error->error_subcode . "): " . $event_data->error->message;
            exit;
        }
        // Store it in an array for later use.
        $events[] = $event_data;
    }

    // We're now done fetching the data from Facebook's Graph API. Now we'll have to create an iCal file.

    // This requires the iCalcreator PHP class, which you can downloead from kigkonsult at kigkonsult.se/iCalcreator/index.php
    require_once("icalcreator/iCalcreator.class.php");

    // Create the calendar, set up some basic properties
    $c = new vcalendar(array('unique_id' => $page));

    $c->setProperty('X-WR-CALNAME', $page . ' events');
    $c->setProperty('X-WR-CALDESC', 'Facebook events for ' . $page);
    $c->setProperty('X-WR-TIMEZONE', $events[0]->timezone); // We assume all of the events use the same timezone.

    // Loop through the events, create event components in the calendar
    foreach($events as $key => $event){
        $e[$key] = & $c->newComponent('vevent');

        $e[$key]->setProperty('summary', $event->name);
        $e[$key]->setProperty('dtstart', $event->start_time);
        $e[$key]->setProperty('dtend', $event->end_time);
        $e[$key]->setProperty('description', $event->description . "\n\nhttp://www.facebook.com/events/" . $event->id);
        $e[$key]->setProperty('location', $event->location);
    }

    // Remove the cache if it exists
    if(file_exists($cache)){
        unlink($cache);
    }

    // Open (create) the cache file
    if(!$handle = fopen($cache, 'w')){
        echo "Cannot open output file: " . $cache;
        exit;
    }

    // Write the calendar to the cache
    if(fwrite($handle, $c->createCalendar()) === FALSE){
        echo "Cannot write to output file: " . $cache;
        exit;
    }

    // Close the cache file
    fclose($handle);
}

// Now we've got the calendar in the cache file, either newly generated and stored there just a few lines ago or from earlier. Now we'll just display it.

header("Content-Type: text/calendar; charset=UTF-8");
header("Content-Disposition: filename=" . $page . ".ics");
require($cache);
?>