Facebook Auth with high traffic sites: empty access tokens, empty /me

Question

We have an app running on a Facebook tab at the moment which is receiving a good deal of traffic. People are signing up every few seconds, and most are successful. However I

Answer 1

I think it's because php_openssl extension is either absent or disabled. See this question to enable it. Or you can use cURL. Take fb_ca_chain_bundle.crt from PHP SDK official (or set CURLOPT_SSL_VERIFYPEER to false):

$base_url = 'https://graph.facebook.com/oauth/access_token';
$params   = array();

$params['client_id']     = $client_id;
$params['client_secret'] = $client_secret;
$params['redirect_uri']  = $redirect_uri;
$params['code']          = $code;

$options = array(
    CURLOPT_SSL_VERIFYHOST => 2,
    CURLOPT_SSL_VERIFYPEER => true,
    CURLOPT_CAINFO         => __DIR__ .'/fb_ca_chain_bundle.crt',
    CURLOPT_RETURNTRANSFER => true,
    CURLINFO_HEADER_OUT    => false,
    CURLOPT_HEADER         => false,
    CURLOPT_URL            => $base_url . '?' . http_build_query($params),
 );

 // Init cURL and send the request
 $ch = curl_init();
 curl_setopt_array($ch, $params);

 $result = curl_exec($ch);
 $infos  = curl_getinfo($ch);

 curl_close($ch);
 var_dump($result, $infos);

EDIT: i warn you this is a quick copy and paste from my code so you would double check $options.