Extracting data from a PHP object

I am using Facebook API and the class creates this object.

   object(User)#4 (5) {
      ["fbc_uid"]=>
      string(9) "324234324"
      ["fbc_first_name"]=>
      string(5) "James"
      ["fbc_last_name"]=>
      string(5) "Proud"
      ["fbc_name"]=>
      string(11) "James Proud"
      ["fbc_email"]=>
      NULL
    }

      

        
        
        
      

    

How to extract fbc_uid from this object from outside of Facebook User class?