How to check if a user installed the app? - php

Question

I have an app on facebook, which is kind of a competition between users. Each user gains points and the one with most points wins.
I keep the IDs of the users in a table in my database. When a user enters the app, there's a script that checks if he is already in the table, and if not, it adds the user id to the table.
Then, I have a page that shows all of the users and how many points they have. I get through the graph api the user's name by his ID, and then shows it on a nice table.
The only problem is: when a user that used the application once deletes it from his installed application on facebook, I can't get his name anymore, and I get an uncaught OAuth exception.
How can I check if the user has installed the app, so I can display his name only if the app is currently installed on his facebook?

Answer 1

Basically, here is what you would need to do.
<?php
include_once("facebook.php");
$facebook = new Facebook(array(
'appId' => YOUR_APP_ID,
'secret' => YOUR_APP_SECRET
));
$user = $facebook->getUser();
try {
$user_profile = $facebook->api('/me');
} catch(FacebookApiException $e) {
$user = null;
}
if($user) {
// authenticated user
$name = $user_profile['name'];
}
This makes an API request for the current logged in user and, provided it fails, catches the exception and sets the $user variable to null. Then you can do a simple check to see if $user exists.
Hopefully this will point you in the right direction.

Answer 2

I would like to suggest to check this client side.
Then when a user returns you can execute this to see if the permissions are still available, and if not request them again:
FB.getLoginStatus(function(response){
if(response.status == 'connected'){
appisinstalled-actonthis();
}else{
// request permissions
FB.login(function(response){
if(response.status == 'connected'){
appisinstalled-actonthis();
}else{
handlethecancelpermissions();
}
});
}
});
Within your appisinstalled-actonthis function you can then add there name and/or profile pic
Just my two cents!