title: Error: Class 'Facebook\FacebookSession' not found with the facebook PHP SDK
body: <p>I am having a hard time with facebook's SDK documentation. I downloaded the SDK from Github and added it into my PHP project.</p>
  
  <p>Here is the file system:</p>
  
  <pre><code>   ├── Facebook
     │   ├── FacebookAuthorizationException.php
     │   ├── FacebookCanvasLoginHelper.php
     │   ├── FacebookClientException.php
     │   ├── FacebookJavaScriptLoginHelper.php
     │   ├── FacebookOtherException.php
     │   ├── FacebookPermissionException.php
     │   ├── FacebookRedirectLoginHelper.php
     │   ├── FacebookRequest.php
     │   ├── FacebookRequestException.php
     │   ├── FacebookResponse.php
     │   ├── FacebookSDKException.php
     │   ├── FacebookServerException.php
     │   ├── FacebookSession.php
     │   ├── FacebookThrottleException.php
     │   ├── GraphLocation.php
     │   ├── GraphObject.php
     │   ├── GraphSessionInfo.php
     │   ├── GraphUser.php
     │   └── fb_ca_chain_bundle.crt
     └── test.php
  </code></pre>
  
  <p>here is my code so far:</p>
  
  <pre><code>use Facebook\FacebookSession;
  use Facebook\FacebookRequest;
  use Facebook\GraphUser;
  use Facebook\FacebookRequestException;
  
  FacebookSession::setDefaultApplication('*******','******');
  
  $helper = new FacebookRedirectLoginHelper('http://isgeek.eu/fb/FaRepost/return.php');
  $loginUrl = $helper-&gt;getLoginUrl();
  // Use the login url on a link or button to redirect to Facebook for authentication
  </code></pre>
  
  <p>I get this error</p>
  
  <pre><code>Fatal error: Class 'Facebook\FacebookSession' not found in /homepages/2/d184071366/htdocs/isgeek/fb/FaRepost/test.php on line 9
  </code></pre>
  
  <p>At updated my PHP version, so the issue does not comme from here. It seems like the PHP files are not found. I read this question (<a href="https://stackoverflow.com/questions/23413854/facebook-sdk-v4-for-php-minimal-example">Facebook SDK v4 for PHP Minimal Example</a>) but it does not help.</p>
  
  <p>Where does this comme from?</p>