postgresql error code

hey 
i want to see database error code in postgresql when some  database connection values are wrong.
i use  $this->db->error() but postgresql not showing error code.
in postgre_driver.php has that function 

PHP Code:

public function error()
    {
        return array('code' => '', 'message' => pg_last_error($this->conn_id));
    } 


i used pg_result_error function but it didnot show me the error codes. 
how can i see error code or how can i set error code in posgresql ?

thanks for helping