howtos

If you have successfully obtained a calendar feed, you should receive some XML looking like this

A fully-formed private event looks something like this

The following steps show you how to grab a feed using Zend Framework's GData package and then grab the appropriate values.

Making changes to your data and accessing private data will require the passing of an authentication token with your requests. You need to make use of the AuthSub Interface to acquire a token.

Acquiring and manipulating tokens
The workflow of the AuthSub authentication process is nicely summarised by Google:

AuthSubRequest - Request an authentication token

The user will be taken to a login screen hosted on Google's end, where they will have to provide their credentials. If successful, they will be redirected back to the callback URL with a 'token' parameter in the URL's query string.

AuthSubSessionToken - acquire a session token
The token returned above is for one-time-use. If you are going to be making multiple token requests, it is more efficient to convert the one-time-use token to a long-lived session token.

Call AuthSubSessionToken using an HTTP GET request to https://www.google.com/accounts/AuthSubSessionToken. The request must also contain an Authorization header.

If the request is successful, Google responds with an HTTP 200 message. The response header will contain the token in the form
Token=ASDF...8976

AuthSubTokenInfo - check the status of a given token
You can check on the status of a token by making an HTTP GET request to https://www.google.com/accounts/AuthSubTokenInfo. The request must also contain an Authorization header.

The successful HTTP 200 response will give you 3 pieces of key information:


Target= http://www.mysite.com
Scope= http://www.google.com/calendar/feeds/yourgoogleacct%40gmail.com/private/full
Secure=true


AuthSubRevokeToken - revoke an active token
At the time of writing, session tokens do not have an expiration time. There may be cases (e.g. security has been compromised, user no longer wishes to use your service) where you wish to revoke a token.

Make an HTTP GET request to https://www.google.com/accounts/AuthSubRevokeToken. The request must also contain an Authorization header.

If the request is successful you will receive an HTTP 200 message.

Things to keep in mind
At the time of writing, Google will only issue 10 session tokens per site per scope. This means you should keep track of, via a database, your users' tokens. They can be re-used each time the user logs in to your application. If you do not wish to store your users' tokens, and wish them to reauthenticate with Google each time they visit your application, be sure to revoke the tokens whenever they log our or if there is a period of inactivity.

Using the Zend Framework

More comprehensive examples and explanations are available here.

AuthSubRequest

AuthSubToken

Making use of your token

AuthSubRevokeToken

The Zend Framework provides a PHP client library package that allows for easy interaction with GData services. Setting up your application to work with the package is simple.

1. Download a copy of the Zend Framework from: http://framework.zend.com/download/tgz
2. Unzip the contents to a folder that will house the Zend library. Note that to have a functioning Zend framework, you only need the contents of the /library/ folder.
3. The library needs to be accessible via PHP's path. You can either set that in php.ini or within your script like so:
   PLAIN TEXT
   PHP:

   1. set_include_path('/path/to/Zend/library/' . PATH_SEPARATOR . get_include_path());