iscrizione via facebook

[cardi_simo]

ciao ragazzi ho un problema con un file chiamato facebook.php, ho scaricato sdk di facebook ma appena mi connetto su index.php mi esce questo errore Fatal error: Cannot redeclare class Facebook in /web/htdocs/www.miosito.it/home/prova/src/facebook.php on line 79

il problema è l'ultimo in fondo, grazie per l'aiuto

questo è il codice php

<?php
require_once "base_facebook.php";
/** * Extends the BaseFacebook class with the intent of using * PHP sessions to store user ids and access tokens. */class Facebook extends BaseFacebook{  /**   * Identical to the parent constructor, except that   * we start a PHP session to store the user ID and   * access token if during the course of execution   * we discover them.   *   * @param Array $config the application configuration.   * @see BaseFacebook::__construct in facebook.php   */  public function __construct($config) {    if (!session_id()) {      session_start();    }    parent::__construct($config);  }
  protected static $kSupportedKeys =    array('state', 'code', 'access_token', 'user_id');
  /**   * Provides the implementations of the inherited abstract   * methods.  The implementation uses PHP sessions to maintain   * a store for authorization codes, user ids, CSRF states, and   * access tokens.   */  protected function setPersistentData($key, $value) {    if (!in_array($key, self::$kSupportedKeys)) {      self::errorLog('Unsupported key passed to setPersistentData.');      return;    }
    $session_var_name = $this->constructSessionVariableName($key);    $_SESSION[$session_var_name] = $value;  }
  protected function getPersistentData($key, $default = false) {    if (!in_array($key, self::$kSupportedKeys)) {      self::errorLog('Unsupported key passed to getPersistentData.');      return $default;    }
    $session_var_name = $this->constructSessionVariableName($key);    return isset($_SESSION[$session_var_name]) ?      $_SESSION[$session_var_name] : $default;  }
  protected function clearPersistentData($key) {    if (!in_array($key, self::$kSupportedKeys)) {      self::errorLog('Unsupported key passed to clearPersistentData.');      return;    }
   $session_var_name = $this->constructSessionVariableName($key);    unset($_SESSION[$session_var_name]);  }
  protected function clearAllPersistentData() {    foreach (self::$kSupportedKeys as $key) {      $this->clearPersistentData($key);    } }
  protected function constructSessionVariableName($key) {    return implode('_', array('fb',                              $this->getAppId(),                              $key));  }}