public static function set_default_avatar($s)
 {
     self::$default_avatar = $s;
 }
 /**
  * magical PHP method
  */
 public function __construct()
 {
     if (self::$facebook_secret == null || self::$facebook_id == null) {
         user_error('Cannot instigate a FacebookCallback object without an application secret and id', E_USER_ERROR);
     }
     parent::__construct();
 }
 public function __construct()
 {
     if (self::$consumer_secret == null || self::$consumer_key == null) {
         user_error('Cannot instigate a TwitterCallback object without a consumer secret and key', E_USER_ERROR);
     }
     parent::__construct();
 }