Make anonymous call with Facebook PHP SDK - php

Question

In my PHP application, users provide their own Facebook Application ID and Application Secret. I need to validate them and display nice error if they are invalid.
I already found a nice way to do it. I can make a request to https://graph.facebook.com/oauth/access_token?client_id=123456&client_secret=abcdefg&grant_type=client_credentials
If credentials are invalid, the response is as follows:
{
"error": {
"message": "Error validating application. Cannot get application info due to a system error.",
"type": "OAuthException",
"code": 101,
"fbtrace_id": "D8oHjJoc2Nc"
}
}
I'm confused about the ways to do it with PHP SDK. There's a neat get() method to make such a request, but I'm not sure how to send request without authorizing the application. This is what I did:
$app = new Facebook\FacebookApp( $app_id, $app_secret );
$access_token = $app->getAccessToken();
$query = http_build_query([
'client_id' => $app_id,
'client_secret' => $app_secret,
'grant_type' => 'client_credentials',
]);
$facebook = new Facebook\Facebook( [
'app_id' => $app_id,
'app_secret' => $app_secret,
'default_graph_version' => '2.5',
] );
$response = $facebook->get( '/oauth/access_token?' . $query, $access_token );
I'm getting the following error:
Unknown path components: /oauth/access_token
But even if it worked, it's strange to call it with any sender credentials. Is it possible to make an "anonymous" Facebook request with PHP SDK?

Answer 1

The SDK implicitly adds the API version number specified to the path in -> get(), so I think that's causing your error here because the underlying call is being made to /2.5/oauth/access_token (fails for me in a browser)
It should be /v2.5/oauth/access_token (works for me in a browser)
Update default_graph_version to v2.5 and try that