如何通过Facebook身份验证以编程方式获取用户数据？

Question

I am able to manually get the user's data, but not programatically.

Using the server side code, as it is, from - https://developers.facebook.com/docs/authentication/

 <?php 

 $app_id = "MY_APP_ID";
 $app_secret = "MY_APP_SECRET";
 $my_url = "ADDRESS_OF_CURRENT_PAGE";

 session_start();
 $code = $_REQUEST["code"];

 if(empty($code)) {
   $_SESSION['state'] = md5(uniqid(rand(), TRUE)); //CSRF protection
   $dialog_url = "https://www.facebook.com/dialog/oauth?client_id=" 
     . $app_id . "&redirect_uri=" . urlencode($my_url) . "&state="
     . $_SESSION['state'];

   echo("<script> top.location.href='" . $dialog_url . "'</script>");
 }

 if($_REQUEST['state'] == $_SESSION['state']) {
   $token_url = "https://graph.facebook.com/oauth/access_token?"
   . "client_id=" . $app_id . "&redirect_uri=" . urlencode($my_url)
   . "&client_secret=" . $app_secret . "&code=" . $code;

   $response = @file_get_contents($token_url);
   $params = null;
   parse_str($response, $params);

   $graph_url = "https://graph.facebook.com/me?access_token=" 
     . $params['access_token'];

   $user = json_decode(file_get_contents($graph_url));
   echo("Hello " . $user->name);
 }
 else {
   echo("The state does not match. You may be a victim of CSRF.");
 }

 ?>

The output is only Hello, the user name does not show up!

I think the problem is with the file_get_contents(), as echo-ing $response has no output, where as $token_url has the appropriate value.

   $response = @file_get_contents($token_url);

• PHP version = 5.2.9
• Error reporting is off, but including this in the code - error_reporting(E_ALL); gives no output.

UPDATE - So, I tried this after 6 months, and it worked. The only thing that has changed since then is my hosting. I was using HostBig before. Lesson - Don't depend on $1/month hosting services, they can't be trusted.

Answer 1

So, I tried this after 6 months, and it worked. The only thing that has changed since then is my hosting. I was using HostBig before.

There was probably something wrong with HostBig's PHP configuration, which disabled the file_get_contents().

UPDATE - I talked to the HostBig guys, and they told me that they have disabled allow_url_fopen, for reasons of safety, and suggested cURL as the safer alternative.

Answer 2

Are you trying to run this code from localhost? If yes, then it wont work. While registering your app on facebook, you must have entered your app's website. Upload the script on server, edit your app_id, secret and the url of script. Then try executing it.

If it doesn't work even then, then try echoing your $dialog_url and $token_url . First manually copy paste your $dialog_url in browser and see what error it gives. If it asks for authentication, authenticate your app. It will get you back to the page. Then try running your $token_url in browser. It will give you the exact response what the server is providing you with.