When user logs in using this FB button. Its session is generated. So I can use PHP API to get any information I want.
I put this code in html body
<script>
window.fbAsyncInit = function() {
FB.init({
appId : <?php echo $facebook->getAppId(); ?>, // App ID
channelUrl : '//WWW.example.com/channel.html', // Channel File
status : true, // check login status
cookie : true, // enable cookies to allow the server to access the session
xfbml : true // parse XFBML
});
// Here we subscribe to the auth.authResponseChange JavaScript event. This event is fired
// for any authentication related change, such as login, logout or session refresh. This means that
// whenever someone who was previously logged out tries to log in again, the correct case below
// will be handled.
FB.Event.subscribe('auth.authResponseChange', function(response) {
// Here we specify what we do with the response anytime this event occurs.
if (response.status === 'connected') {
// The response object is returned with a status field that lets the app know the current
// login status of the person. In this case, we're handling the situation where they
// have logged in to the app.
testAPI();
} else if (response.status === 'not_authorized') {
// In this case, the person is logged into Facebook, but not into the app, so we call
// FB.login() to prompt them to do so.
// In real-life usage, you wouldn't want to immediately prompt someone to login
// like this, for two reasons:
// (1) JavaScript created popup windows are blocked by most browsers unless they
// result from direct interaction from people using the app (such as a mouse click)
// (2) it is a bad experience to be continually prompted to login upon page load.
FB.login();
} else {
// In this case, the person is not logged into Facebook, so we call the login()
// function to prompt them to do so. Note that at this stage there is no indication
// of whether they are logged into the app. If they aren't then they'll see the Login
// dialog right after they log in to Facebook.
// The same caveats as above apply to the FB.login() call here.
FB.login();
}
});
};
// Load the SDK asynchronously
(function(d){
var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
if (d.getElementById(id)) {return;}
js = d.createElement('script'); js.id = id; js.async = true;
js.src = "https://connect.facebook.net/en_US/all.js";
ref.parentNode.insertBefore(js, ref);
}(document));
// Here we run a very simple test of the Graph API after login is successful.
// This testAPI() function is only called in those cases.
function testAPI() {
console.log('Welcome! Fetching your information.... ');
FB.api('/me', function(response) {
console.log('Good to see you, ' + response.name + '.');
});
}
</script>
PHP Side Code
$config = array();
$config['appId'] = 'myappid';
$config['secret'] = 'myappsecretid';
$config['fileUpload'] = false; // optional
$facebook = new Facebook($config);
$access_token = FALSE;
$user = $facebook->getUser();
if($user){
// The user is logged in
try{
$user_profile = $facebook->api('/me');
$access_token = $facebook->getAccessToken();
// Here : API call succeeded,
// you have a valid access token
print_r($user_profile); // all the user info is in this object
}
catch(FacebookApiException $e){
// Here : API call failed,
// you don't have a valid access token
// you have to send him to $facebook->getLoginUrl()
$user = null;
}
}