Facebook login with PHP

Last updated on July 7, 2017

Create a Facebook App

Installation

Now head over to your project folder and , run below command.

$ mkdir fb-php-login
$ cd fb-php-login
$ composer require facebook/graph-sdk

Above composer command will pull the Facebook PHP SDK into your project directory under vendor folder.

Now create a file called fb-config.php with below code

 APP_id, // Replace {app-id} with your app id
  'app_secret' => APP_SECRET,
  'default_graph_version' => 'v2.2',
  ]);

Now create a file called login.php to show login link.

 APP_id, // Replace {app-id} with your app id
  'app_secret' => APP_SECRET,
  'default_graph_version' => 'v2.2',
  ]);

Lets create a file called fb-callback.php with below code, we will redirect to this callback URL after user login dialog is called.

getRedirectLoginHelper();

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($accessToken)) {
  if ($helper->getError()) {
    header('HTTP/1.0 401 Unauthorized');
    echo "Error: " . $helper->getError() . "\n";
    echo "Error Code: " . $helper->getErrorCode() . "\n";
    echo "Error Reason: " . $helper->getErrorReason() . "\n";
    echo "Error Description: " . $helper->getErrorDescription() . "\n";
  } else {
    header('HTTP/1.0 400 Bad Request');
    echo 'Bad request';
  }
  exit;
}

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

// The OAuth 2.0 client handler helps us manage access tokens
$oAuth2Client = $fb->getOAuth2Client();

// Get the access token metadata from /debug_token
$tokenMetadata = $oAuth2Client->debugToken($accessToken);
echo '
Metadata
';
var_dump($tokenMetadata);

// Validation (these will throw FacebookSDKException's when they fail)
$tokenMetadata->validateAppId(APP_id); // Replace {app-id} with your app id
// If you know the user ID this access token belongs to, you can validate it here
//$tokenMetadata->validateUserId('123');
$tokenMetadata->validateExpiration();

if (! $accessToken->isLongLived()) {
  // Exchanges a short-lived access token for a long-lived one
  try {
    $accessToken = $oAuth2Client->getLongLivedAccessToken($accessToken);
  } catch (Facebook\Exceptions\FacebookSDKException $e) {
    echo "
Error getting long-lived access token: " . $helper->getMessage() . "
\n\n";
    exit;
  }

  echo '
Long-lived
';
  var_dump($accessToken->getValue());
}

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

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