auth.php

<?php
/**
 * Created by JetBrains PhpStorm.
 * User: nagkumar
 * Date: 14/11/13
 * Time: 11:20 AM
 * To change this template use File | Settings | File Templates.
 */

// Change these
define('API_KEY',      'YOUR_API_KEY_GOES_HERE '                                          );
define('API_SECRET',   'YOUR_API_SECRET_KEY_GOES_HERE'                                       );
define('REDIRECT_URI', 'COMPLETE_URL_TO_success.php');
define('SCOPE',        'r_basicprofile'                        );

// You'll probably use a database
session_name('linkedin');
session_start();

// OAuth 2 Control Flow
if (isset($_GET['error'])) {
    // LinkedIn returned an error
    print $_GET['error'] . ': ' . $_GET['error_description'];
    exit;
} elseif (isset($_GET['code'])) {
    // User authorized your application
    if ($_SESSION['state'] == $_GET['state']) {
        // Get token so you can make API calls
        getAccessToken();
    } else {
        // CSRF attack? Or did you mix up your states?
        exit;
    }
} else {
    if ((empty($_SESSION['expires_at'])) || (time() > $_SESSION['expires_at'])) {
        // Token has expired, clear the state
        $_SESSION = array();
    }
    if (empty($_SESSION['access_token'])) {
        // Start authorization process
        getAuthorizationCode();
    }
}

// Congratulations! You have a valid token. Now fetch your profile
$user = fetch('GET', '/v1/people/~:(firstName,lastName)');
print "Hello $user->firstName $user->lastName.";
exit;

function getAuthorizationCode() {
    $params = array('response_type' => 'code',
        'client_id' => API_KEY,
        'scope' => SCOPE,
        'state' => uniqid('', true), // unique long string
        'redirect_uri' => REDIRECT_URI,
    );

    // Authentication request
    $url = 'https://www.linkedin.com/uas/oauth2/authorization?' . http_build_query($params);

    // Needed to identify request when it returns to us
    $_SESSION['state'] = $params['state'];

    // Redirect user to authenticate
    header("Location: $url");
    exit;
}

function getAccessToken() {
    $params = array('grant_type' => 'authorization_code',
        'client_id' => API_KEY,
        'client_secret' => API_SECRET,
        'code' => $_GET['code'],
        'redirect_uri' => REDIRECT_URI,
    );

    // Access Token request
    $url = 'https://www.linkedin.com/uas/oauth2/accessToken?' . http_build_query($params);

    // Tell streams to make a POST request
    $context = stream_context_create(
        array('http' =>
        array('method' => 'POST',
        )
        )
    );

    // Retrieve access token information
    $response = file_get_contents($url, false, $context);

    // Native PHP object, please
    $token = json_decode($response);

    // Store access token and expiration time
    $_SESSION['access_token'] = $token->access_token; // guard this!
    $_SESSION['expires_in']   = $token->expires_in; // relative time (in seconds)
    $_SESSION['expires_at']   = time() + $_SESSION['expires_in']; // absolute time

    return true;
}

function fetch($method, $resource, $body = '') {
    $params = array('oauth2_access_token' => $_SESSION['access_token'],
        'format' => 'json',
    );

    // Need to use HTTPS
    $url = 'https://api.linkedin.com' . $resource . '?' . http_build_query($params);
    // Tell streams to make a (GET, POST, PUT, or DELETE) request
    $context = stream_context_create(
        array('http' =>
        array('method' => $method,
        )
        )
    );


    // Hocus Pocus
    $response = file_get_contents($url, false, $context);

    // Native PHP object, please
    return json_decode($response);
}