Facebook API documentation continued

Face2

In the first half, I covered the initial steps to getting your first facebook app running, and got as far as unpacking the standard sample app onto the server.

The next step is to customize the sample app with the technical information about what SQL database you’re using, and how to uniquely identify your app to facebook. To make these changes, you’ll need to edit the config.php file in the facebook-platform/footprints/ folder. I did this by logging into the server with ssh, and then loading the file in emacs within the shell.

To get the values for the $api_key and $secret variables in your config.php, you’ll need to go to http://www.facebook.com/developers/ (not developers.facebook.com as it says in the file), specifically the setup new application link. Once you’ve followed the setup process, you should see the two values you need in the My Applications section of the developer application.

Next, you’ll need to create an sql database for the sample app to store its information. Most hosting companies offer some number of mysql databases, and have a control panel to add them. In dreamhost’s case, they’re held on a different servers than the file system, so I had to create a subdomain and wait for the DNS propagation again.

Once you’ve created a database, you’ll need to create a table to hold the sample app’s data. Luckily the SQL code is included in the config.php file, so you should just be able to locate a console or mysql shell in your control panel, or through running mysql after ssh-ing into the server, and paste the code right in there.

You’ll also need to create a user, and make a note of the database name, user name and password so you can add them to config.php. The last thing you’ll need is an ip address for your database. This was problematic for me, since on dreamhost the sql server is on a different machine than the PHP is running on, so I couldn’t just use the local host address, 127.0.0.1. The IP address of the SQL machine is not guaranteed, so I should probably use DNS lookup to resolve it dynamically, but for testing I just checked what the current IP address of it was using ping and then statically set it to that in config.php.

Once all of that information was set up, I then made sure I had a callback URL set up in the facebook applications settings. This should point to the public address of your application folder, so something like http://somehost.com/facebook-platform/footprints/

Now, if you type that same address into your browser, you should see a page asking you to log into facebook. Once you log in, you should then see the default footprints application page, or a descriptive error. One really nice thing about the facebook system is that they include a bunch of developer information describing the cause of an error in more detail in the HTML comments of most error pages, if you’re the developer of the application. To look at this, view the source and you should see something near the top, very handy!

Have a play around, hopefully you should be able to plant footprints on your friends, and then view your database and see entries added to the table.

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