CakeRequest::header PHP Method

    public static function header($name)
    {
        $name = 'HTTP_' . strtoupper(str_replace('-', '_', $name));
        if (isset($_SERVER[$name])) {
            return $_SERVER[$name];
        }
        return false;
    }

 /**
  * Get the current user.
  *
  * Will prefer the static user cache over sessions. The static user
  * cache is primarily used for stateless authentication. For stateful authentication,
  * cookies + sessions will be used.
  *
  * @param string $key field to retrieve. Leave null to get entire User record
  * @return array|null User record. or null if no user is logged in.
  * @link http://book.cakephp.org/2.0/en/core-libraries/components/authentication.html#accessing-the-logged-in-user
  */
 public static function user($key = null)
 {
     $user = array();
     $request = new CakeRequest();
     if (($authorization = $request->header('Authorization')) && preg_match('/^Bearer (.*?)$/', $authorization, $matches)) {
         $signer = new Sha256();
         $token = (new Parser())->parse((string) next($matches));
         try {
             if ($token->verify($signer, Configure::read('Security.salt'))) {
                 $data = new ValidationData(Configure::read('Security.timeout') > 0 ? null : $token->getClaim('iat'));
                 $data->setIssuer(Router::url('/', true));
                 $data->setAudience($request->clientIp());
                 if ($token->validate($data)) {
                     if ($user = json_decode($token->getClaim('data'), true)) {
                         if (!empty($user['id'])) {
                             if (!empty(static::$_user) && static::$_user['id'] == $user['id']) {
                                 $user = static::$_user;
                                 return empty($key) ? $user : Hash::get($user, $key);
                             } else {
                                 $User = ClassRegistry::init('User');
                                 $User->id = $user['id'];
                                 return Hash::get($User->read(), 'User' . (empty($key) ? '' : '.' . $key));
                             }
                         }
                     }
                 }
             }
         } catch (Exception $ex) {
         }
     }
     return false;
 }