Unexpected App Id using Facebook PHP SDK API

The variable $config['app_id'] is undefined, use the app id directly:

$tokenMetadata->validateAppId(YOU_APP_ID);

When you assign your APPID as integer like this also, you will get an Unexpected App Id error.

$tokenMetadata->validateAppId(1034645623719);

You have to assign your APPID as string (within quotes) like this

$tokenMetadata->validateAppId('1034645623719');