FACEBOOK API : How do I get the long-lived access token from PHP API

Question

My question: how to get long-lived access token from PHP API. I have read through all the prior posts about this matter and still don't have the answer. Basically, I get a short-lived access token from the API explorer. Subsquently, I wrote a simple PHP prohgram invoking the facebook graph API to request a long-lived access token. Yet, it isn't working. I am missing something here. Here is the snippet of the PHP code that I wrote:

  $response = $fb->request("GET", "GET /oauth/access_token?  
    grant_type=fb_exchange_token&           
    client_id={my app id}&
    client_secret={my app secret}&
    fb_exchange_token={'the short-lived token obtained from the api 
   explorer'}")
    ..//error checking...
      //

    // then I call this:
    $token = $response->getaccessToken();
   // end of program

It turns out the getaccessToken() return the same short-lived token that I passed to the API. So, I am running of idea of how to make it work.

According to the API doc, the call with the input parameter of "fb_exhcnage_token" is supposed to return a "long-lived access token". Yet, I am not getting it.

Answer 1

This is valid in 2019, after long-term tokens became 60-day expiries. Here are Facebook's instructions to swap a short-term token (provided in front-end) for a long-term token (server only):

https://developers.facebook.com/docs/facebook-login/access-tokens/refreshing/

Generate a Long-lived User or Page Access Token
You will need the following:

A valid User or Page Access Token
Your App ID
Your App Secret
Query the GET oath/access_token endpoint.

curl -i -X GET "https://graph.facebook.com/{graph-api-version}/oauth/access_token?  
    grant_type=fb_exchange_token           
    client_id={app-id}&
    client_secret={app-secret}&
    fb_exchange_token={your-access-token}" 

Sample Response
{
  "access_token":"{long-lived-access-token}",
  "token_type": "bearer",
  "expires_in": 5183944            //The number of seconds until the token expires
}

You can make this curl request in PHP using curl_init() :

https://www.php.net/manual/en/book.curl.php

---

Or if you would rather use the Facebook PHP SDK, you can do this:

1.) Create a FB request object with your credentials. 2.) Request long-term token using the FB object and the access token

public function createFacebookRequestObject($facebookUser)
    {
        try {
            return new Facebook([
                'app_id' => config('env.FACEBOOK_GRAPH_API_ID'),
                'app_secret' => config('env.FACEBOOK_GRAPH_API_SECRET'),
                'default_graph_version' => 'v4.0',
                'default_access_token' => $facebookUser->access_token
            ]);
        } catch (\Facebook\Exceptions\FacebookSDKException $e) {
            return 'Facebook SDK returned an error: ' . $e->getMessage();
        }
    }

public function fetchLongTermAccessToken($fb, $facebookUser)
        {
            return $fb->get(
                "/oauth/access_token?grant_type=
                fb_exchange_token&fb_exchange_token=" 
              . $facebookUser['access_token']  
                . '&client_id=' 
                . config('env.FACEBOOK_APP_ID'), );
        }