Facebook API: Check User Permissions

Here is a simple function (modified from a class I wrote to simplify Facebook API calls) to check if there are discrepencies between the scope of the Facebook app and the permissions granted by the user.

function checkPermissions($scope, $facebook)
{
    // Break the scope into an array
    $scope = array_map('trim', explode(",", $scope));
    // Get the users permissions from Facebook and put them in an array
    $getUserPerms = $facebook->api('/me/permissions');
    $userPerms = array_keys($getUserPerms['data'][0]);
    // Permissions not granted is the difference between these arrys
    $ungrantedPerms = array_diff($scope, $userPerms);
    if ( ! empty($ungrantedPerms)) {
        // authenticate user again
    }
}

It assumes you have your scope defined in the following format:

$scope = 'email, user_about_me, user_likes, manage_pages, publish_stream';

For a more object oriented approach you could do something like:

// Assuming we have an instance of the facebook library and the scope stored
private $facebook;
private $scope;
/**
 * Return an array of the permissions that haven't been granted.
 */
private function ungrantedPermissions()
{
    $scope = $this->scope;
    // Break the scope into an array
    $scope = array_map('trim', explode(",", $scope));
    // Get the users permissions from Facebook and put them in an array
    $getUserPerms = $this->facebook->api('/me/permissions');
    $userPerms = array_keys($getUserPerms['data'][0]);
    // Permissions not granted is the difference between these arrys
    return array_diff($scope, $userPerms);
}