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access_token_from_javascript.md

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Getting Access Token From The JavaScript SDK Example

This example covers obtaining an access token and signed request from the Facebook JavaScript SDK with the Facebook SDK for PHP.

Example

In order to have the JavaScript SDK set a cookie containing a signed request (which contains information about the logged in user), you must first initialize the JavaScript SDK with the {cookie: true} option.

<html>
<body>

<p><a href="#" onClick="logInWithFacebook()">Log In with the JavaScript SDK</a></p>

<script>
  logInWithFacebook = function() {
    FB.login(function(response) {
      if (response.authResponse) {
        alert('You are logged in & cookie set!');
        // Now you can redirect the user or do an AJAX request to
        // a PHP script that grabs the signed request from the cookie.
      } else {
        alert('User cancelled login or did not fully authorize.');
      }
    });
    return false;
  };
  window.fbAsyncInit = function() {
    FB.init({
      appId: 'your-app-id',
      cookie: true, // This is important, it's not enabled by default
      version: 'v2.10'
    });
  };

  (function(d, s, id){
    var js, fjs = d.getElementsByTagName(s)[0];
    if (d.getElementById(id)) {return;}
    js = d.createElement(s); js.id = id;
    js.src = "//connect.facebook.net/en_US/sdk.js";
    fjs.parentNode.insertBefore(js, fjs);
  }(document, 'script', 'facebook-jssdk'));
</script>
</body>
</html>

After the user successfully logs in, redirect the user (or make an AJAX request) to a PHP script that obtains an access token from the signed request that exists in the cookie.

# /js-login.php
$fb = new Facebook\Facebook([
  'app_id' => '{app-id}',
  'app_secret' => '{app-secret}',
  'default_graph_version' => 'v2.10',
  ]);

$helper = $fb->getJavaScriptHelper();

try {
  $accessToken = $helper->getAccessToken();
} catch(Facebook\Exceptions\FacebookResponseException $e) {
  // When Graph returns an error
  echo 'Graph returned an error: ' . $e->getMessage();
  exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
  // When validation fails or other local issues
  echo 'Facebook SDK returned an error: ' . $e->getMessage();
  exit;
}

if (! isset($accessToken)) {
  echo 'No cookie set or no OAuth data could be obtained from cookie.';
  exit;
}

// Logged in
echo '<h3>Access Token</h3>';
var_dump($accessToken->getValue());

$_SESSION['fb_access_token'] = (string) $accessToken;

// User is logged in!
// You can redirect them to a members-only page.
//header('Location: https://example.com/members.php');