Today Facebook ended support for v2.2 of the API, and v2.3 includes a change to the format of access tokens which broke the ‘Add Link to Facebook’ plugin and generates the access token error above.
After a little debugging, I found a fix by editing the add-link-to-facebook-int.php file:
Replace
static function Process_fb_token($response) {
$key = 'access_token=';
$access_token = substr($response, strpos($response, $key) + strlen($key));
$access_token = explode('&', $access_token);
$access_token = $access_token[0];
return $access_token;
}
with
static function Process_fb_token($response) {
$key = 'access_token=';
$access_token = json_decode($response)->access_token;
// $access_token = substr($response, strpos($response, $key) + strlen($key));
// $access_token = explode('&', $access_token);
// $access_token = $access_token[0];
return $access_token;
}