Facebook session not being created - php

Question

I am using this code to post to the user's wall :
require 'fb/src/facebook.php';
$facebook = new Facebook(array(
'appId' => 'xxx',
'secret' => 'xxx',
));
$params = array(
'canvas' => 1,
'scope' => 'publish_stream,email,user_about_me,user_birthday,user_website',
'redirect_uri' => 'urlhere',
);
$fb_session = $facebook->getUser();
// Session based API call.
if ($fb_session)
{
try
{
$args = array(
'message' => $_GET['by'],
'link' => 'linkhere/',
'caption' => $_GET['test']
);
$post_id = $facebook->api("/me/feed", "post", $args);
}
catch (Exception $e)
{
$fb_login_url = $facebook->getLoginUrl($params);
echo $e->getMessage();
}
}
else
{
$fb_login_url = $facebook->getLoginUrl($params);
}
The code is working till the point uuer clicks on login part to post. After that the url contains a code = xxxzz and a state =yyy but the $fb_session is 0.
This works sometimes without any changes. Please help!

Answer 1

You should include the access token when you try to post to some User Facebook wall.
First get access token:
$fbToken = NULL;
$fbToken = $facebook->getAccessToken();
right after $fb_session = $facebook->getUser();
and then include it in the $args array:
'access_token' => $fbToken
if session is NOT created or access token is not valid, you should redirect the user back to re-authorize your Facebook App.
So in ELSE, you should add
header("Location: $fb_login_url ");
after $fb_login_url = $facebook->getLoginUrl($params);
assuming that everything else is correct, but the access_token is not valid, you should also include header("Location: $fb_login_url "); before echo $e->getMessage();

Answer 2

in both cases you are using getloginurl
shouldn't it be
if ($fb_session) {
try {
$args = array(
'message' => $_GET['by'],
'link' => 'linkhere/',
'caption' => $_GET['test']
);
$post_id = $facebook->api("/me/feed", "post", $args);
} catch (Exception $e) {
$fb_logout_url = $facebook->getLogoutUrl;
.
.
.