Check if the user is a fan of my facebook page? - php

Question

I used to use the flowing code to check if the user is a fan of my page or not while he is on my facebook page. Now I want to check if the user is a fan of my facebook page while he is on my WEBSITE.
<?php
$signed_request = $_REQUEST["signed_request"];
list($encoded_sig, $payload) = explode('.', $signed_request, 2);
$data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);
if (empty($data["page"]["liked"])) {
echo "You are not a fan!";
} else {
echo "Welcome back fan!";
}
?>
I read through the facebook documentation, but I was not able to find suitable answer.
Help ?
I do not want to deal with any application permissions with facebook. How can I approach this through only php ?

Answer 1

You will not get page details if visiting application not in Page Tab.
You may achieve that with simple FQL query to page_fan table (knowing the id of the Facebook Page of course):
SELECT uid, page_id FROM page_fan WHERE uid=me() AND page_id=PAGE_ID
Or by querying Graph API for likes connection of user object:
https://graph.facebook.com/me/likes/PAGE_ID
Both of those ways require user_likes permission granted by user.
To get the same details for user's friends ask for friends_likes permission and substitute me/me() with friend id.
Update: (just to describe what you asked in comments)
There are cases that requiring user_likes may be unnecessary due to nature of flow, if you only need to know that user will/need to like some URL and/or Facebook Page.
You may do so by subscribing (FB.subscribe) to edge.create event which will be triggered once user will like the page (for un-like there is edge.remove event).
Beware that this is only reliable in cases user didn't liked that content before since edge.create only fired on time of user's action.

Answer 2

A better approach to the problem is:
// to generate user access token after the user is logged in
$USER_ACCESS_TOKEN = $facebook->getExtendedAccessToken();
$isFan = curl("https://api.facebook.com/method/pages.isFan?format=json&access_token=" . $USER_ACCESS_TOKEN . "&page_id=" . $FACEBOOK_PAGE_ID);
function curl($url) {
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
$data = curl_exec($ch);
curl_close($ch);
return $data;
}