如何从Facebook Graph Api获得名字

This is the graph api code by which i am getting fullname, email and facebook id.. what i need is to get only first name of a user by graph api but i have no clue to how to do that? any help with it.

$request = new FacebookRequest($sess, 'GET', '/me');
    // from response get graph object
    $response = $request->execute();
    $graph = $response->getGraphObject(GraphUser::className());
    // use graph object methods to get user details

    $graphObject = $response->getGraphObject();

    $fuid = $graphObject->getProperty('id');   // To Get Facebook ID
    $ffname = $graphObject->getProperty('name'); // To Get Facebook full name
    $femail = $graphObject->getProperty('email'); //email

Like this?

$firstName = $graphObject->getProperty('first_name');

If you still don´t get it, try with another API call:

/me?fields=first_name

You can modify your code including all the fields you need including first_name for example the following code including id, full name, first name, last name and email

$request = new FacebookRequest( $session, 'GET', '/me?fields=id,name,first_name,last_name,email' );
$response = $request->execute();
// get response
$graphObject = $response->getGraphObject();
$fbfirstname = $graphObject->getProperty('first_name'); // get Facebook first name